Refactor to manager-centric model, add team calendar for all users

Key changes:
- Removed office-centric model (deleted offices.py, office-rules)
- Renamed to team-rules, managers are part of their own team
- Team calendar visible to all (read-only for employees)
- Admins can have a manager assigned

compose.yml

@@ -1,7 +1,7 @@
 services:
   parking:
     build: .
-    container_name: parking-manager
+    container_name: parking
     restart: unless-stopped
     ports:
       - "8000:8000"
@@ -26,9 +26,10 @@ services:
       timeout: 10s
       retries: 3
       start_period: 10s
+    networks:
+      - org-network
 
-# For production with external network (Caddy/Authelia):
-# networks:
-#   default:
-#     external: true
-#     name: proxy
+networks:
+  org-network:
+    external: true
+    name: org-stack_org-network