feat: Add database explorer page with SQLite management

- Add /database page with table explorer, query executor and stats
- Implement MCP tools: list_tables, get_table_schema, get_table_data,
  get_database_stats, execute_query
- Add database API endpoints with security (SELECT only)
- Add database icon to toolbar

frontend/src/services/toolRegistry.ts

@@ -24,8 +24,13 @@ import {
   unregisterProjectCanvasTools,
   PROJECT_CANVAS_TOOLS
 } from './tools/projectCanvasTools'
+import {
+  registerDatabaseTools,
+  unregisterDatabaseTools,
+  DATABASE_TOOLS
+} from './tools/databaseTools'
 
-type PageName = 'home' | 'canvas' | 'components' | 'themes' | 'projects' | 'project-canvas'
+type PageName = 'home' | 'canvas' | 'components' | 'themes' | 'projects' | 'project-canvas' | 'database'
 
 interface PageToolSet {
   register: () => void
@@ -85,6 +90,11 @@ const pageTools: Record<PageName, PageToolSet> = {
     register: registerThemeTools,
     unregister: unregisterThemeTools,
     toolNames: THEME_TOOLS
+  },
+  database: {
+    register: registerDatabaseTools,
+    unregister: unregisterDatabaseTools,
+    toolNames: DATABASE_TOOLS
   }
 }