feat: implement location events & error handling (Step 10.2)

- Add LocationService with create/rename/archive methods
- Add LocationProjection for event handling
- Add admin-only location management routes at /locations
- Add error response helpers (error_response, error_toast, success_toast)
- Add toast handler JS to base template for HX-Trigger notifications
- Update seeds.py to emit LocationCreated events per spec §23
- Archived locations block animal moves with 422 error

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

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

PLAN.md

@@ -379,19 +379,19 @@ Check off items as completed. Each phase builds on the previous.
 - [x] E2E test #6: Deletes: recorder vs admin cascade (test_e2e_deletion.py)
 - [x] E2E test #7: Harvest with yields (test_e2e_harvest.py)
 - [x] E2E test #8: Optimistic lock with confirm (test_e2e_optimistic_lock.py)
-- [ ] **Commit checkpoint**
+- [x] **Commit checkpoint** (5ba068b)
 
 NOTE: Tests #1-5 in test_e2e_stats_progression.py have documented discrepancies with
 spec values due to integer truncation of bird-days and timeline differences. The
 tests verify implementation consistency, not exact spec values.
 
 ### Step 10.2: Location Events & Error Handling
-- [ ] Implement LocationCreated (idempotent for seeding)
-- [ ] Implement LocationRenamed
-- [ ] Implement LocationArchived
-- [ ] Standardize error responses (422, 409, 401/403)
-- [ ] Toast via HX-Trigger
-- [ ] Write tests for location events and error rendering
+- [x] Implement LocationCreated (idempotent for seeding)
+- [x] Implement LocationRenamed
+- [x] Implement LocationArchived
+- [x] Standardize error responses (422, 409, 401/403)
+- [x] Toast via HX-Trigger
+- [x] Write tests for location events and error rendering
 - [ ] **Commit checkpoint**
 
 ### Step 10.3: CLI, Docker & Deployment