feat(dashboard): redesign with active bookings, calendar, and compact stats

Major Dashboard improvements focusing on active reservations and calendar view:

Frontend changes:
- Add ActiveBookings component showing in-progress bookings with progress bars
- Add DashboardCalendar component with read-only calendar view of all user bookings
- Refactor Dashboard layout: active bookings → stats grid → calendar → activity
- Remove redundant Quick Actions and Available Spaces sections
- Make Quick Stats compact (36px icons, 20px font) and clickable (router-link)
- Add datetime utility functions (isBookingActive, getBookingProgress, formatRemainingTime)
- Fix MyBookings to read status query parameter from URL
- Auto-refresh active bookings every 60s with proper cleanup

Backend changes:
- Add GET /api/bookings/my/calendar endpoint with date range filtering
- Fix Google Calendar sync in reschedule_booking and admin_update_booking
- Add Google OAuth environment variables to .env.example

Design:
- Dark mode compatible with CSS variables throughout
- Mobile responsive (768px breakpoint, 2-column stats grid)
- CollapsibleSection pattern for all dashboard sections
- Progress bars with accent colors for active bookings

Performance:
- Optimized API calls (calendar uses date range filtering)
- Remove duplicate calendar data loading on mount
- Computed property caching for stats and filtered bookings
- Memory leak prevention (setInterval cleanup on unmount)

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

backend/.env.example

@@ -17,3 +17,8 @@ SMTP_USER=
 SMTP_PASSWORD=
 SMTP_FROM_ADDRESS=noreply@space-booking.local
 SMTP_ENABLED=false
+
+# Google Calendar Integration
+GOOGLE_CLIENT_ID=your_google_client_id_here
+GOOGLE_CLIENT_SECRET=your_google_client_secret_here
+GOOGLE_REDIRECT_URI=https://your-domain.com/api/integrations/google/callback

backend/app/api/bookings.py

@@ -12,7 +12,11 @@ from app.models.space import Space
 from app.models.user import User
 from app.services.audit_service import log_action
 from app.services.email_service import send_booking_notification
-from app.services.google_calendar_service import create_calendar_event, delete_calendar_event
+from app.services.google_calendar_service import (
+    create_calendar_event,
+    delete_calendar_event,
+    update_calendar_event,
+)
 from app.services.notification_service import create_notification
 from app.schemas.booking import (
     AdminCancelRequest,
@@ -202,6 +206,37 @@ def get_my_bookings(
     return [BookingWithSpace.model_validate(b) for b in bookings]
 
 
+@bookings_router.get("/my/calendar", response_model=list[BookingWithSpace])
+def get_my_bookings_calendar(
+    start: Annotated[datetime, Query(description="Start datetime (ISO format)")],
+    end: Annotated[datetime, Query(description="End datetime (ISO format)")],
+    db: Annotated[Session, Depends(get_db)],
+    current_user: Annotated[User, Depends(get_current_user)],
+) -> list[BookingWithSpace]:
+    """
+    Get user's bookings for calendar view within date range.
+
+    Query parameters:
+    - **start**: Start datetime in ISO format (e.g., 2024-01-01T00:00:00)
+    - **end**: End datetime in ISO format (e.g., 2024-01-31T23:59:59)
+
+    Returns bookings with status approved or pending, sorted by start time.
+    """
+    bookings = (
+        db.query(Booking)
+        .join(Space, Booking.space_id == Space.id)
+        .filter(
+            Booking.user_id == current_user.id,
+            Booking.start_datetime < end,
+            Booking.end_datetime > start,
+            Booking.status.in_(["approved", "pending"]),
+        )
+        .order_by(Booking.start_datetime)
+        .all()
+    )
+    return [BookingWithSpace.model_validate(b) for b in bookings]
+
+
 @bookings_router.post("", response_model=BookingResponse, status_code=status.HTTP_201_CREATED)
 def create_booking(
     booking_data: BookingCreate,
@@ -873,6 +908,15 @@ def admin_update_booking(
             detail=errors[0],
         )
 
+    # Sync with Google Calendar if event exists
+    if booking.google_calendar_event_id:
+        update_calendar_event(
+            db=db,
+            booking=booking,
+            user_id=int(booking.user_id),  # type: ignore[arg-type]
+            event_id=booking.google_calendar_event_id,
+        )
+
     # Log audit
     log_action(
         db=db,
@@ -1025,6 +1069,15 @@ def reschedule_booking(
     booking.start_datetime = data.start_datetime  # type: ignore[assignment]
     booking.end_datetime = data.end_datetime  # type: ignore[assignment]
 
+    # Sync with Google Calendar if event exists
+    if booking.google_calendar_event_id:
+        update_calendar_event(
+            db=db,
+            booking=booking,
+            user_id=int(booking.user_id),  # type: ignore[arg-type]
+            event_id=booking.google_calendar_event_id,
+        )
+
     # Log audit
     log_action(
         db=db,