feat(ledger): service CRUD for postings and three new routes

add_posting / update_posting / delete_posting all go through
ensure_editable(month), so closed months reject posting mutations
with the same lifecycle guard as every other mutation. Negative
amounts are allowed for refunds / corrections. Dates are parsed as
ISO (YYYY-MM-DD) but not constrained to the month for now.

update_month_entry loses the applied keyword; the route no longer
accepts an applied form field. applied is derived only from now
on. Three new routes wire the ledger:

  POST   /month/{ym}/entries/{entry_id}/postings
  POST   /month/{ym}/postings/{posting_id}
  DELETE /month/{ym}/postings/{posting_id}

Each returns the updated section partial plus OOB swaps for the
zero widget and all four group totals, same pattern the existing
mutations use.

Refs #19

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/quartermaster/month_service.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 import re
 from dataclasses import dataclass
 from datetime import date, datetime, timezone
-from decimal import Decimal
+from decimal import Decimal, InvalidOperation
 from enum import Enum
 
 from sqlalchemy import select
@@ -24,6 +24,7 @@ from quartermaster.models import (
     MonthDebtTarget,
     MonthEntry,
     MonthState,
+    Posting,
     Section,
 )
 
@@ -125,7 +126,6 @@ def create_month(db: Session, year_month: str) -> Month:
             section=e.section,
             name=e.name,
             planned=e.amount,
-            applied=Decimal("0.00"),
             notes=e.notes,
             origin_name=e.name,
             origin_planned=e.amount,
@@ -238,7 +238,6 @@ def add_month_entry(
         section=section,
         name=name.strip(),
         planned=planned,
-        applied=Decimal("0.00"),
         notes=_clean_notes(notes),
         origin_name=None,
         origin_planned=None,
@@ -277,7 +276,6 @@ def update_month_entry(
     *,
     name: str | None = None,
     planned: Decimal | None = None,
-    applied: Decimal | None = None,
     notes: str | None | object = _NOTES_SENTINEL,
 ) -> MonthEntry | None:
     entry = get_month_entry(db, month, entry_id)
@@ -287,8 +285,6 @@ def update_month_entry(
         entry.name = name.strip()
     if planned is not None:
         entry.planned = planned
-    if applied is not None:
-        entry.applied = applied
     if notes is not _NOTES_SENTINEL:
         entry.notes = _clean_notes(notes)  # type: ignore[arg-type]
     db.commit()
@@ -296,6 +292,85 @@ def update_month_entry(
     return entry
 
 
+def add_posting(
+    db: Session,
+    month: Month,
+    entry_id: int,
+    occurred_on: date,
+    amount: Decimal,
+    description: str | None = None,
+    payee: str | None = None,
+) -> Posting | None:
+    entry = get_month_entry(db, month, entry_id)
+    if entry is None:
+        return None
+    posting = Posting(
+        month_entry_id=entry.id,
+        occurred_on=occurred_on,
+        amount=amount,
+        description=_clean_notes(description),
+        payee=_clean_notes(payee),
+    )
+    db.add(posting)
+    db.commit()
+    db.refresh(posting)
+    return posting
+
+
+def get_posting(
+    db: Session, month: Month, posting_id: int
+) -> Posting | None:
+    posting = db.get(Posting, posting_id)
+    if posting is None:
+        return None
+    # Ensure posting belongs to this month via its entry
+    if posting.entry is None or posting.entry.month_id != month.id:
+        return None
+    return posting
+
+
+_POSTING_SENTINEL = object()
+
+
+def update_posting(
+    db: Session,
+    month: Month,
+    posting_id: int,
+    *,
+    occurred_on: date | None = None,
+    amount: Decimal | None = None,
+    description: str | None | object = _POSTING_SENTINEL,
+    payee: str | None | object = _POSTING_SENTINEL,
+) -> Posting | None:
+    posting = get_posting(db, month, posting_id)
+    if posting is None:
+        return None
+    if occurred_on is not None:
+        posting.occurred_on = occurred_on
+    if amount is not None:
+        posting.amount = amount
+    if description is not _POSTING_SENTINEL:
+        posting.description = _clean_notes(description)  # type: ignore[arg-type]
+    if payee is not _POSTING_SENTINEL:
+        posting.payee = _clean_notes(payee)  # type: ignore[arg-type]
+    db.commit()
+    db.refresh(posting)
+    return posting
+
+
+def delete_posting(
+    db: Session, month: Month, posting_id: int
+) -> MonthEntry | None:
+    """Delete a posting; return the parent entry so callers can re-render its section."""
+    posting = get_posting(db, month, posting_id)
+    if posting is None:
+        return None
+    entry = posting.entry
+    db.delete(posting)
+    db.commit()
+    return entry
+
+
 def get_month_target(db: Session, month: Month) -> MonthDebtTarget:
     if month.target is not None:
         return month.target

src/quartermaster/routes_month.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from datetime import date
 from decimal import Decimal, InvalidOperation
 
 from fastapi import APIRouter, Depends, Form, HTTPException, Request
@@ -242,7 +243,6 @@ def update_month_entry(
     request: Request,
     name: str | None = Form(None),
     planned: str | None = Form(None),
-    applied: str | None = Form(None),
     notes: str | None = Form(None),
     db: Session = Depends(get_session),
 ) -> HTMLResponse:
@@ -253,11 +253,9 @@ def update_month_entry(
         if not clean_name:
             raise HTTPException(status_code=400, detail="name must not be empty")
     parsed_planned = _parse_amount(planned) if planned is not None else None
-    parsed_applied = _parse_amount(applied) if applied is not None else None
     kwargs: dict = dict(
         name=clean_name,
         planned=parsed_planned,
-        applied=parsed_applied,
     )
     if notes is not None:
         kwargs["notes"] = notes
@@ -320,6 +318,109 @@ def reopen_month(
     )
 
 
+def _parse_date(raw: str) -> date:
+    try:
+        return date.fromisoformat(raw.strip())
+    except (ValueError, AttributeError) as exc:
+        raise HTTPException(
+            status_code=400, detail="date must be YYYY-MM-DD"
+        ) from exc
+
+
+def _parse_signed_amount(raw: str) -> Decimal:
+    try:
+        amount = Decimal(raw.strip())
+    except (InvalidOperation, AttributeError) as exc:
+        raise HTTPException(
+            status_code=400, detail="amount must be numeric"
+        ) from exc
+    return amount.quantize(Decimal("0.01"))
+
+
+@router.post("/entries/{entry_id}/postings", response_class=HTMLResponse)
+def create_posting(
+    year_month: str,
+    entry_id: int,
+    request: Request,
+    occurred_on: str = Form(...),
+    amount: str = Form(...),
+    description: str | None = Form(None),
+    payee: str | None = Form(None),
+    db: Session = Depends(get_session),
+) -> HTMLResponse:
+    month = _require_editable_month(db, year_month)
+    posting = month_service.add_posting(
+        db,
+        month,
+        entry_id,
+        _parse_date(occurred_on),
+        _parse_signed_amount(amount),
+        description=description,
+        payee=payee,
+    )
+    if posting is None:
+        raise HTTPException(status_code=404, detail="entry not found")
+    db.refresh(month)
+    entry = month_service.get_month_entry(db, month, entry_id)
+    return _append_oob(
+        _render_section(request, month, entry.section),
+        _render_zero(request, month),
+        _render_group_totals(request, month),
+    )
+
+
+@router.post("/postings/{posting_id}", response_class=HTMLResponse)
+def update_posting(
+    year_month: str,
+    posting_id: int,
+    request: Request,
+    occurred_on: str | None = Form(None),
+    amount: str | None = Form(None),
+    description: str | None = Form(None),
+    payee: str | None = Form(None),
+    db: Session = Depends(get_session),
+) -> HTMLResponse:
+    month = _require_editable_month(db, year_month)
+    kwargs: dict = {}
+    if occurred_on is not None:
+        kwargs["occurred_on"] = _parse_date(occurred_on)
+    if amount is not None:
+        kwargs["amount"] = _parse_signed_amount(amount)
+    if description is not None:
+        kwargs["description"] = description
+    if payee is not None:
+        kwargs["payee"] = payee
+    updated = month_service.update_posting(db, month, posting_id, **kwargs)
+    if updated is None:
+        raise HTTPException(status_code=404, detail="posting not found")
+    db.refresh(month)
+    entry = updated.entry
+    return _append_oob(
+        _render_section(request, month, entry.section),
+        _render_zero(request, month),
+        _render_group_totals(request, month),
+    )
+
+
+@router.delete("/postings/{posting_id}", response_class=HTMLResponse)
+def delete_posting(
+    year_month: str,
+    posting_id: int,
+    request: Request,
+    db: Session = Depends(get_session),
+) -> HTMLResponse:
+    month = _require_editable_month(db, year_month)
+    entry = month_service.delete_posting(db, month, posting_id)
+    if entry is None:
+        raise HTTPException(status_code=404, detail="posting not found")
+    db.refresh(month)
+    return _append_oob(
+        _render_section(request, month, entry.section),
+        _render_zero(request, month),
+        _render_group_totals(request, month),
+    )
+
+
 @router.post("/target", response_class=HTMLResponse)
 def update_month_target(
     year_month: str,