fix(ui): condense add-entry to a compact disclosure trigger

Every section used to end with a wide horizontal add form (name
input, amount input, button, notes input spanning the row). It took
up more horizontal real estate than the entries themselves. Now the
form is wrapped in a <details class="add-entry"> whose summary is a
small tracked-caps link ("+ add fixed amount bills"). Click to
reveal the same form below; HTMX submission still resets and hides
on success.

Same treatment on the budget page sections and the month page
sections.

Refs #19

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

src/quartermaster/static/app.css

@@ -421,6 +421,40 @@ tr.add-row td {
   display: block;
 }
 
+/* Add-entry disclosure: collapsed trigger, expanded form */
+details.add-entry { margin: 0; }
+details.add-entry > summary {
+  list-style: none;
+  cursor: pointer;
+  user-select: none;
+  display: inline-block;
+  padding: 0.1rem 0.25rem;
+}
+details.add-entry > summary::-webkit-details-marker { display: none; }
+details.add-entry .add-trigger {
+  font-family: var(--sans);
+  font-size: 0.78rem;
+  font-weight: 500;
+  color: var(--muted);
+  letter-spacing: 0.18em;
+  text-transform: uppercase;
+  border-bottom: 1px dashed transparent;
+  padding-bottom: 1px;
+  transition: color 0.12s ease, border-color 0.12s ease;
+}
+details.add-entry > summary:hover .add-trigger {
+  color: var(--ink);
+  border-bottom-color: var(--rule);
+}
+details.add-entry[open] > summary .add-trigger {
+  color: var(--ink);
+  border-bottom-color: var(--ink);
+}
+details.add-entry > .add-form,
+details.add-entry > .month-add-form {
+  margin-top: 0.45rem;
+}
+
 .entry-name {
   font-family: var(--sans);
   font-weight: 500;

src/quartermaster/templates/partials/month_section.html

@@ -203,6 +203,8 @@
     {% endfor %}
     {% if editable %}
       <div class="add-row">
+        <details class="add-entry">
+          <summary><span class="add-trigger">+ add {{ section.label|lower }}</span></summary>
           <form
             class="add-form month-add-form"
             hx-post="/month/{{ month.year_month }}/sections/{{ section.section.value }}/entries"
@@ -215,6 +217,7 @@
             <button type="submit">Add</button>
             <input class="notes-input add-notes" type="text" name="notes" placeholder="notes (optional)">
           </form>
+        </details>
       </div>
     {% endif %}
   </div>

src/quartermaster/templates/partials/section.html

@@ -44,6 +44,8 @@
       {% endfor %}
       <tr class="add-row">
         <td colspan="4">
+          <details class="add-entry">
+            <summary><span class="add-trigger">+ add {{ section.label|lower }}</span></summary>
             <form
               class="add-form"
               hx-post="/sections/{{ section.section.value }}/entries"
@@ -56,6 +58,7 @@
               <button type="submit">Add</button>
               <input class="notes-input add-notes" type="text" name="notes" placeholder="notes (optional)">
             </form>
+          </details>
         </td>
       </tr>
     </tbody>