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.

shared/types.ts

@@ -0,0 +1,14 @@
+export type JobStatus = 'pending' | 'running' | 'completed' | 'failed' | 'stopped';
+
+export interface AppUser {
+  id: string;
+  email: string;
+  displayName: string;
+  avatarUrl?: string | null;
+  createdAt: string;
+  updatedAt: string;
+}
+
+export interface SessionUser extends AppUser {
+  sessionId: string;
+}