feat: migrate app to local Fastify and Postgres stack

Replace Supabase auth and search runtime with a local Fastify API, PostgreSQL/PostGIS schema, and local session handling. Scaffold the worker and deep-research foundations while keeping the existing research, dashboard, and map flows running on the new backend.

src/vite-env.d.ts

@@ -1,8 +1,7 @@
 /// <reference types="vite/client" />
 
 interface ImportMetaEnv {
-  readonly VITE_SUPABASE_URL: string;
-  readonly VITE_SUPABASE_ANON_KEY: string;
+  readonly VITE_API_BASE_URL: string;
   readonly VITE_GOOGLE_MAPS_PLATFORM_KEY: string;
 }