fix: migrate AI chat system from Firebase/Firestore to Postgres

Firebase was not configured so every chat request crashed with
'Firebase Admin credentials not configured'.

- chat-mode-resolver.ts: read project phase from fs_projects (Postgres)
- chat-context.ts: load project data from fs_projects instead of Firestore
- /api/ai/conversation: store/retrieve conversations in chat_conversations
  Postgres table (created automatically on first use)
- /api/ai/chat: replace all Firestore reads/writes with Postgres queries
- v_ai_chat/page.tsx: replace Firebase client auth with useSession from
  next-auth/react; remove Firestore listeners, use REST API for project data

Co-authored-by: Cursor <cursoragent@cursor.com>

app/[workspace]/project/[projectId]/v_ai_chat/page.tsx

@@ -9,15 +9,13 @@ import { Input } from "@/components/ui/input";
 import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
 import { Send, Loader2, Paperclip, X, FileText, RotateCcw, Upload, CheckCircle2, AlertTriangle, Sparkles } from "lucide-react";
 import { cn } from "@/lib/utils";
-import { auth } from "@/lib/firebase/config";
+import { useSession } from "next-auth/react";
 import { toast } from "sonner";
 import { GitHubRepoPicker } from "@/components/ai/github-repo-picker";
 import { PhaseSidebar } from "@/components/ai/phase-sidebar";
 import { CollapsibleSidebar } from "@/components/ui/collapsible-sidebar";
 import { ExtractionResultsEditable } from "@/components/ai/extraction-results-editable";
 import type { ChatExtractionData } from "@/lib/ai/chat-extraction-types";
-import { db } from "@/lib/firebase/config";
-import { doc, onSnapshot, getDoc } from "firebase/firestore";
 import { VisionForm } from "@/components/ai/vision-form";
 
 interface Message {
@@ -72,6 +70,7 @@ export default function GettingStartedPage() {
   const params = useParams();
   const projectId = params.projectId as string;
   const workspace = params.workspace as string;
+  const { status: sessionStatus } = useSession();
   
   const [messages, setMessages] = useState<Message[]>([]);
   const [input, setInput] = useState("");
@@ -104,74 +103,45 @@ export default function GettingStartedPage() {
     messagesEndRef.current?.scrollIntoView({ behavior: 'smooth' });
   }, [messages]);
 
-  // Check for vision answers on load
+  // Load project phase + vision answers from the Postgres-backed API
   useEffect(() => {
     if (!projectId) return;
 
-    const checkVision = async () => {
+    const loadProject = async () => {
       try {
-        const projectDoc = await getDoc(doc(db, "projects", projectId));
-        if (projectDoc.exists()) {
-          const data = projectDoc.data();
-          const hasAnswers = data?.visionAnswers?.allAnswered === true;
+        const res = await fetch(`/api/projects/${projectId}`);
+        if (res.ok) {
+          const data = await res.json();
+          const phase = data.project?.currentPhase || 'collector';
+          setCurrentPhase(phase);
+          const hasAnswers = data.project?.visionAnswers?.allAnswered === true;
           setHasVisionAnswers(hasAnswers);
         }
       } catch (error) {
-        console.error('Error checking vision answers:', error);
+        console.error('Error loading project:', error);
       } finally {
         setCheckingVision(false);
       }
     };
 
-    checkVision();
-  }, [projectId]);
-
-  // Listen to project phase changes
-  useEffect(() => {
-    if (!projectId) return;
-
-    const unsubscribe = onSnapshot(
-      doc(db, "projects", projectId),
-      (snapshot) => {
-        if (snapshot.exists()) {
-          const data = snapshot.data();
-          const phase = data?.currentPhase || "collector";
-          setCurrentPhase(phase);
-          
-          // Update vision answers status
-          const hasAnswers = data?.visionAnswers?.allAnswered === true;
-          setHasVisionAnswers(hasAnswers);
-        }
-      }
-    );
-
-    return () => unsubscribe();
+    loadProject();
   }, [projectId]);
 
   // Initialize with AI welcome message
   useEffect(() => {
-    if (!isInitialized && projectId) {
-      const unsubscribe = auth.onAuthStateChanged(async (user) => {
-        if (!user) {
-          // Not signed in, trigger AI welcome
+    if (!isInitialized && projectId && sessionStatus !== 'loading') {
+      const initialize = async () => {
+        if (sessionStatus === 'unauthenticated') {
           setIsLoading(false);
           setIsInitialized(true);
-          setTimeout(() => {
-            sendChatMessage("Hello");
-          }, 500);
+          setTimeout(() => sendChatMessage("Hello"), 500);
           return;
         }
 
-        // User is signed in, load conversation history first
+        // Signed in via NextAuth — load conversation history
         try {
-          const token = await user.getIdToken();
-          
           // Fetch existing conversation history
-          const historyResponse = await fetch(`/api/ai/conversation?projectId=${projectId}`, {
-            headers: {
-              'Authorization': `Bearer ${token}`,
-            },
-          });
+          const historyResponse = await fetch(`/api/ai/conversation?projectId=${projectId}`);
           
           let existingMessages: Message[] = [];
           
@@ -231,11 +201,11 @@ export default function GettingStartedPage() {
           setIsLoading(false);
           setIsInitialized(true);
         }
-      });
+      };
 
-      return () => unsubscribe();
+      initialize();
     }
-  }, [projectId, isInitialized]);
+  }, [projectId, isInitialized, sessionStatus]);
 
   const sendChatMessage = async (messageContent: string) => {
     const content = messageContent.trim();
@@ -251,24 +221,10 @@ export default function GettingStartedPage() {
     setIsSending(true);
 
     try {
-      const user = auth.currentUser;
-      if (!user) {
-        toast.error('Please sign in to continue');
-        setIsSending(false);
-        return;
-      }
-
-      const token = await user.getIdToken();
       const response = await fetch('/api/ai/chat', {
         method: 'POST',
-        headers: {
-          'Authorization': `Bearer ${token}`,
-          'Content-Type': 'application/json',
-        },
-        body: JSON.stringify({
-          projectId,
-          message: content,
-        }),
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ projectId, message: content }),
       });
 
       if (!response.ok) {
@@ -392,21 +348,8 @@ export default function GettingStartedPage() {
     }
 
     try {
-      const user = auth.currentUser;
-      if (!user) {
-        toast.error('Please sign in to reset chat');
-        return;
-      }
-
-      const token = await user.getIdToken();
-      
-      const response = await fetch('/api/ai/conversation/reset', {
-        method: 'POST',
-        headers: {
-          'Authorization': `Bearer ${token}`,
-          'Content-Type': 'application/json',
-        },
-        body: JSON.stringify({ projectId }),
+      const response = await fetch(`/api/ai/conversation?projectId=${projectId}`, {
+        method: 'DELETE',
       });
 
       if (response.ok) {
@@ -433,20 +376,9 @@ export default function GettingStartedPage() {
       setExtractionStatus("importing");
       setExtractionError(null);
 
-      const user = auth.currentUser;
-      if (!user) {
-        toast.error("Please sign in to import chats");
-        setIsImporting(false);
-        return;
-      }
-
-      const token = await user.getIdToken();
       const importResponse = await fetch(`/api/projects/${projectId}/knowledge/import-ai-chat`, {
         method: "POST",
-        headers: {
-          "Content-Type": "application/json",
-          Authorization: `Bearer ${token}`,
-        },
+        headers: { "Content-Type": "application/json" },
         body: JSON.stringify({
           title: extractForm.title || "Imported AI chat",
           provider: extractForm.provider,