feat: Add mobile responsive layout, open room access, and admin room management

Mobile Responsive Layout:
- Add useMediaQuery, useIsMobile, useIsTablet, useIsDesktop hooks for device detection
- Create MobileHeader component with hamburger menu and action drawer
- Create BottomToolbar for mobile navigation (Files, Members)
- Create SlidePanel component for full-screen mobile sidebars
- Update RoomDetail.tsx with mobile/desktop conditional rendering
- Update RoomList.tsx with single-column grid and touch-friendly buttons
- Add CSS custom properties for safe areas and touch targets (min 44px)
- Add mobile viewport meta tags for notched devices

Open Room Access:
- All authenticated users can view all rooms (not just their own)
- Users can join active rooms they're not members of
- Add is_member field to room responses
- Update room list API to return all rooms by default

Admin Room Management:
- Add permanent delete functionality for system admins
- Add delete confirmation dialog with room title verification
- Broadcast room deletion via WebSocket to connected users
- Add users search API for adding members

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/modules/file_storage/models.py

@@ -13,8 +13,8 @@ class RoomFile(Base):
     # Primary key
     file_id = Column(String(36), primary_key=True)
 
-    # Foreign key to incident room
-    room_id = Column(String(36), ForeignKey("incident_rooms.room_id"), nullable=False)
+    # Foreign key to incident room (CASCADE delete when room is permanently deleted)
+    room_id = Column(String(36), ForeignKey("incident_rooms.room_id", ondelete="CASCADE"), nullable=False)
 
     # File metadata
     uploader_id = Column(String(255), nullable=False)