feat: add per-space timezone settings and improve booking management

- Add timezone configuration per space with fallback to system default
- Implement timezone-aware datetime display and editing across frontend
- Add migration for per_space_settings table
- Update booking service to handle timezone conversions properly
- Improve .gitignore to exclude build artifacts
- Add comprehensive testing documentation

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

backend/app/api/bookings.py

@@ -248,6 +248,7 @@ def create_booking(
         user_id=user_id,
         start_datetime=start_datetime_utc,
         end_datetime=end_datetime_utc,
+        user_timezone=user_timezone,
     )
 
     if errors:
@@ -344,6 +345,9 @@ def create_recurring_booking(
 
     duration = timedelta(minutes=data.duration_minutes)
 
+    # Get user timezone
+    user_timezone = current_user.timezone or "UTC"
+
     # Generate occurrence dates
     occurrences = []
     current_date = data.start_date
@@ -360,18 +364,23 @@ def create_recurring_booking(
 
     # Create bookings for each occurrence
     for occurrence_date in occurrences:
-        # Build datetime
+        # Build datetime in user timezone
         start_datetime = datetime.combine(occurrence_date, time(hour, minute))
         end_datetime = start_datetime + duration
 
+        # Convert to UTC for validation and storage
+        start_datetime_utc = convert_to_utc(start_datetime, user_timezone)
+        end_datetime_utc = convert_to_utc(end_datetime, user_timezone)
+
         # Validate
         user_id = int(current_user.id)  # type: ignore[arg-type]
         errors = validate_booking_rules(
             db=db,
             space_id=data.space_id,
-            start_datetime=start_datetime,
-            end_datetime=end_datetime,
+            start_datetime=start_datetime_utc,
+            end_datetime=end_datetime_utc,
             user_id=user_id,
+            user_timezone=user_timezone,
         )
 
         if errors:
@@ -387,14 +396,14 @@ def create_recurring_booking(
                 # Skip and continue
                 continue
 
-        # Create booking
+        # Create booking (store UTC times)
         booking = Booking(
             user_id=user_id,
             space_id=data.space_id,
             title=data.title,
             description=data.description,
-            start_datetime=start_datetime,
-            end_datetime=end_datetime,
+            start_datetime=start_datetime_utc,
+            end_datetime=end_datetime_utc,
             status="pending",
             created_at=datetime.utcnow(),
         )
@@ -491,6 +500,7 @@ def update_booking(
         end_datetime=updated_end,  # type: ignore[arg-type]
         user_id=user_id,
         exclude_booking_id=booking.id,  # Exclude self from overlap check
+        user_timezone=user_timezone,
     )
 
     if errors:
@@ -662,6 +672,8 @@ def approve_booking(
         )
 
     # Re-validate booking rules to prevent race conditions
+    # Use booking owner's timezone for validation
+    user_timezone = booking.user.timezone or "UTC" if booking.user else "UTC"
     errors = validate_booking_rules(
         db=db,
         space_id=int(booking.space_id),  # type: ignore[arg-type]
@@ -669,6 +681,7 @@ def approve_booking(
         start_datetime=booking.start_datetime,  # type: ignore[arg-type]
         end_datetime=booking.end_datetime,  # type: ignore[arg-type]
         exclude_booking_id=int(booking.id),  # type: ignore[arg-type]
+        user_timezone=user_timezone,
     )
 
     if errors:
@@ -842,6 +855,8 @@ def admin_update_booking(
         booking.end_datetime = data.end_datetime  # type: ignore[assignment]
 
     # Re-validate booking rules
+    # Use booking owner's timezone for validation
+    user_timezone = booking.user.timezone or "UTC" if booking.user else "UTC"
     errors = validate_booking_rules(
         db=db,
         space_id=int(booking.space_id),  # type: ignore[arg-type]
@@ -849,6 +864,7 @@ def admin_update_booking(
         end_datetime=booking.end_datetime,  # type: ignore[arg-type]
         user_id=int(booking.user_id),  # type: ignore[arg-type]
         exclude_booking_id=booking.id,  # Exclude self from overlap check
+        user_timezone=user_timezone,
     )
 
     if errors:
@@ -987,6 +1003,8 @@ def reschedule_booking(
     old_end = booking.end_datetime
 
     # Validate new time slot
+    # Use booking owner's timezone for validation
+    user_timezone = booking.user.timezone or "UTC" if booking.user else "UTC"
     errors = validate_booking_rules(
         db=db,
         space_id=int(booking.space_id),  # type: ignore[arg-type]
@@ -994,6 +1012,7 @@ def reschedule_booking(
         end_datetime=data.end_datetime,
         user_id=int(booking.user_id),  # type: ignore[arg-type]
         exclude_booking_id=booking.id,  # Exclude self from overlap check
+        user_timezone=user_timezone,
     )
 
     if errors: