Add self-hosted deployment configuration

- Add backend entry point (cmd/server/main.go)
- Add prompt=select_account to Google OAuth flow
- Add combined init.sql for self-hosted PostgreSQL
- Update docker-compose to include backend service with memory limits

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -15,6 +15,7 @@ services:
     volumes:
       - postgres_data:/var/lib/postgresql/data
       - ./backend/scripts/init.sql:/docker-entrypoint-initdb.d/init.sql
+    command: postgres -c shared_buffers=128MB -c max_connections=50
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}"]
       interval: 10s
@@ -24,7 +25,7 @@ services:
   redis:
     image: redis:7-alpine
     container_name: realtime-collab-redis
-    command: ["redis-server", "--appendonly", "yes"]
+    command: ["redis-server", "--appendonly", "yes", "--maxmemory", "64mb", "--maxmemory-policy", "allkeys-lru"]
     ports:
       - "6379:6379"
     volumes:
@@ -35,6 +36,22 @@ services:
       timeout: 3s
       retries: 5
 
+  backend:
+    build:
+      context: ./backend
+      dockerfile: Dockerfile
+    container_name: realtime-collab-backend
+    env_file:
+      - ./backend/.env
+    ports:
+      - "8080:8080"
+    depends_on:
+      postgres:
+        condition: service_healthy
+      redis:
+        condition: service_healthy
+    restart: unless-stopped
+
 volumes:
   postgres_data:
   redis_data: