feat: add email, scheduler, and Zulip integration services

- Add email service for sending meeting invites with ICS attachments
- Add scheduler for background calendar sync jobs
- Add Zulip service for meeting notifications
- Make ics_url optional for participants
- Add /api/schedule endpoint with 2-hour lead time validation
- Update frontend to support scheduling flow

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -8,7 +8,7 @@ services:
     volumes:
       - postgres_data:/var/lib/postgresql/data
     ports:
-      - "5432:5432"
+      - "5433:5432"
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -U postgres"]
       interval: 5s
@@ -22,8 +22,10 @@ services:
     environment:
       DATABASE_URL: postgresql+asyncpg://postgres:postgres@db:5432/availability
       SYNC_DATABASE_URL: postgresql://postgres:postgres@db:5432/availability
+    env_file:
+      - .env
     ports:
-      - "8000:8000"
+      - "8001:8000"
     depends_on:
       db:
         condition: service_healthy
@@ -36,9 +38,9 @@ services:
       context: ./frontend
       dockerfile: Dockerfile
     ports:
-      - "5173:8080"
+      - "5174:8080"
     environment:
-      VITE_API_URL: http://localhost:8000
+      VITE_API_URL: http://localhost:8001
     depends_on:
       - backend
     volumes: