feat: implement Feed Quick Capture form (Step 7.4)

Add /feed page with tabbed forms for Give Feed and Purchase Feed:
- GET /feed renders page with tabs (Give Feed default, Purchase Feed)
- POST /actions/feed-given records feed given to a location
- POST /actions/feed-purchased records feed purchases to inventory

Also adopts idiomatic FastHTML/HTMX pattern:
- Add hx-boost to base template for automatic AJAX on forms
- Refactor egg form to use action/method instead of hx_post

Spec §22 compliance:
- Integer kg only, min=1
- Warn if inventory negative (but allow)
- Toast + stay on page after submit
- Location/type stick, amount resets to default bag size

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

PLAN.md

@@ -279,14 +279,15 @@ Check off items as completed. Each phase builds on the previous.
 - [x] Write tests: form renders, POST creates event, validation errors (422)
 - [x] **Commit checkpoint** (e9804cd)
 
-### Step 7.4: Feed Quick Capture
-- [ ] Create `web/routes/feed.py`:
-  - [ ] GET /feed - Feed Quick Capture form
-  - [ ] POST /actions/feed-given
-  - [ ] POST /actions/feed-purchased
-- [ ] Create `web/templates/feed.py` with forms
-- [ ] Implement defaults per spec §22
-- [ ] Write tests: form renders, POST creates events, blocked without purchase
+### Step 7.4: Feed Quick Capture ✓
+- [x] Create `web/routes/feed.py`:
+  - [x] GET /feed - Feed Quick Capture form
+  - [x] POST /actions/feed-given
+  - [x] POST /actions/feed-purchased
+- [x] Create `web/templates/feed.py` with forms
+- [x] Implement defaults per spec §22
+- [x] Write tests: form renders, POST creates events, blocked without purchase
+- [x] Adopt hx-boost pattern (idiomatic FastHTML/HTMX)
 - [ ] **Commit checkpoint**
 
 ### Step 7.5: Move Animals