feat(db): add nullable notes column to entry and month_entry

Free-text annotation up to 1024 chars. Nullable so existing rows need
no backfill; an empty or whitespace-only input will be normalised to
NULL in the service layer. Alembic batch_alter_table handles the
SQLite table rebuild automatically.

Refs #13

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

alembic/versions/ec804bdf366d_add_notes_column_to_entry_and_month_.py

@@ -0,0 +1,42 @@
+"""add notes column to entry and month_entry
+
+Revision ID: ec804bdf366d
+Revises: 03ebe3c07262
+Create Date: 2026-04-17 12:47:41.533978
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = 'ec804bdf366d'
+down_revision: Union[str, Sequence[str], None] = '03ebe3c07262'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table('entry', schema=None) as batch_op:
+        batch_op.add_column(sa.Column('notes', sa.String(length=1024), nullable=True))
+
+    with op.batch_alter_table('month_entry', schema=None) as batch_op:
+        batch_op.add_column(sa.Column('notes', sa.String(length=1024), nullable=True))
+
+    # ### end Alembic commands ###
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    # ### commands auto generated by Alembic - please adjust! ###
+    with op.batch_alter_table('month_entry', schema=None) as batch_op:
+        batch_op.drop_column('notes')
+
+    with op.batch_alter_table('entry', schema=None) as batch_op:
+        batch_op.drop_column('notes')
+
+    # ### end Alembic commands ###

src/quartermaster/models.py

@@ -51,6 +51,7 @@ class Entry(Base):
     )
     name: Mapped[str] = mapped_column(String(128), nullable=False)
     amount: Mapped[Decimal] = mapped_column(Numeric(10, 2), nullable=False)
+    notes: Mapped[str | None] = mapped_column(String(1024), nullable=True)
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True), server_default=func.now(), nullable=False
     )
@@ -117,6 +118,7 @@ class MonthEntry(Base):
         Numeric(10, 2), nullable=False, default=Decimal("0.00"),
         server_default="0.00",
     )
+    notes: Mapped[str | None] = mapped_column(String(1024), nullable=True)
     origin_name: Mapped[str | None] = mapped_column(String(128), nullable=True)
     origin_planned: Mapped[Decimal | None] = mapped_column(
         Numeric(10, 2), nullable=True