fix(chat): improve OpenCode Zen integration and error handling

- Fetch models dynamically from OpenCode Zen API (36 models vs 5 hardcoded)
- Add function calling support check before using tools
- Add retry logic (num_retries=2) for transient failures
- Improve logging for debugging API calls and errors
- Update system prompt for multi-stop itinerary context
- Clean up unused imports in frontend components
- Remove deleted views.py (moved to views/__init__.py)

frontend/src/routes/+error.svelte

@@ -52,8 +52,7 @@
 						class="link link-primary"
 						target="_blank"
 						rel="noopener noreferrer"
-						href="https://github.com/Alex-Wiesner/voyage"
-						>documentation</a
+						href="https://github.com/Alex-Wiesner/voyage">documentation</a
 					>.
 				</p>
 			</div>