feat: implement web UI for provider and model configuration

- Added 'provider_configs' and 'model_configs' tables to database.
- Refactored ProviderManager to support thread-safe dynamic updates and database overrides.
- Implemented 'Models' tab in dashboard to manage model visibility, mapping, and pricing.
- Added provider configuration modal to 'Providers' tab.
- Integrated database overrides into chat completion logic (enabled state, mapping, and cost).

static/index.html

@@ -89,6 +89,10 @@
                         <i class="fas fa-server"></i>
                         <span>Providers</span>
                     </a>
+                    <a href="#models" class="menu-item" data-page="models" data-tooltip="Manage Models">
+                        <i class="fas fa-cube"></i>
+                        <span>Models</span>
+                    </a>
                     <a href="#monitoring" class="menu-item" data-page="monitoring" data-tooltip="Live Monitoring">
                         <i class="fas fa-heartbeat"></i>
                         <span>Real-time Monitoring</span>
@@ -168,6 +172,7 @@
     <script src="/js/pages/costs.js"></script>
     <script src="/js/pages/clients.js"></script>
     <script src="/js/pages/providers.js"></script>
+    <script src="/js/pages/models.js"></script>
     <script src="/js/pages/monitoring.js"></script>
     <script src="/js/pages/settings.js"></script>
     <script src="/js/pages/logs.js"></script>