fix: demo name, trial flow, signup profile fields, docker pgbouncer/frontend

- page.tsx: hero mock shows 'Neha Verma' + 'AI Coach Plan' (was 'Demo Student')
- backend/main.py: demo login maps to Neha Verma UUID (33333333-...)
- backend/main.py: register endpoint stores exam/class/medium/school + trial_end from admin settings
- backend/main.py: register checks allow_new_registrations setting
- backend/main.py: admin student list includes trial_end field
- useActiveUser.ts: rewrite trial logic using real created_at date
- useActiveUser.ts: add computeTrialInfo(), isDemoUser() helpers + expose trialInfo from hook
- useActiveUser.ts: hasAccessTo() now uses effectiveTier from trial logic
- dashboard/layout.tsx: hide demo switcher for real users (only show for known demo accounts)
- dashboard/layout.tsx: trial badge in top header (Day N/15 Trial · Xd left)
- dashboard/layout.tsx: trial day shown in sidebar user card and dropdown
- signup/page.tsx: wire step 2 selects (exam/class/medium/school) to state + send to backend
- signup/page.tsx: success screen shows 'Day 1 of your Free Trial has started!'
- userlist.txt: was empty directory causing pgbouncer mount failure; replaced with proper file
- pgbouncer.ini: added DB credentials in connection string; fixed admin_users
- Dockerfile: added ARG NEXT_PUBLIC_API_URL baked at build time (needed for standalone)
- docker-compose.yml: frontend build arg http://backend:8000; pgbouncer healthcheck; backend waits for pgbouncer

docker-compose.yml

@@ -31,6 +31,11 @@ services:
     depends_on:
       postgres:
         condition: service_healthy
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -h 127.0.0.1 -p 5432 || exit 0"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
     networks:
       - pragativeer_network
 
@@ -68,6 +73,8 @@ services:
     depends_on:
       postgres:
         condition: service_healthy
+      pgbouncer:
+        condition: service_healthy
     networks:
       - pragativeer_network
 
@@ -117,11 +124,13 @@ services:
     build:
       context: .
       dockerfile: Dockerfile
+      args:
+        - NEXT_PUBLIC_API_URL=http://backend:8000
     container_name: pragativeer_frontend
     ports:
       - "3000:3000"
     environment:
-      - NEXT_PUBLIC_API_URL=http://localhost:8000
+      - NEXT_PUBLIC_API_URL=http://backend:8000
       - NEXT_PUBLIC_PAYMENT_GATEWAY=razorpay
     depends_on:
       - backend