migrate: replace Firebase with PostgreSQL across core routes

- chat-context.ts: session history now from fs_sessions
- /api/sessions: reads from fs_sessions (NextAuth session auth)
- /api/github/connect: NextAuth session + stores in fs_users.data
- /api/user/api-key: NextAuth session + stores in fs_users.data
- /api/projects/[id]/vision: PATCH to fs_projects JSONB
- /api/projects/[id]/knowledge/items: reads from fs_knowledge_items
- /api/projects/[id]/knowledge/import-ai-chat: uses pg createKnowledgeItem
- lib/server/knowledge.ts: fully rewritten to use PostgreSQL
- entrypoint.sh: add fs_knowledge_items and chat_conversations tables

Made-with: Cursor

app/api/projects/[projectId]/knowledge/import-ai-chat/route.ts

@@ -1,5 +1,7 @@
 import { NextResponse } from 'next/server';
-import { getAdminDb } from '@/lib/firebase/admin';
+import { getServerSession } from 'next-auth';
+import { authOptions } from '@/lib/auth/authOptions';
+import { query } from '@/lib/db-postgres';
 import { createKnowledgeItem } from '@/lib/server/knowledge';
 import type { KnowledgeSourceMeta } from '@/lib/types/knowledge';
 
@@ -32,9 +34,12 @@ export async function POST(
       return NextResponse.json({ error: 'transcript is required' }, { status: 400 });
     }
 
-    const adminDb = getAdminDb();
-    const projectSnap = await adminDb.collection('projects').doc(projectId).get();
-    if (!projectSnap.exists) {
+    const session = await getServerSession(authOptions);
+    if (!session?.user?.email) {
+      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
+    }
+    const projectRows = await query(`SELECT id FROM fs_projects WHERE id = $1 LIMIT 1`, [projectId]);
+    if (projectRows.length === 0) {
       return NextResponse.json({ error: 'Project not found' }, { status: 404 });
     }