Fix QA findings: single UNION query, weekly validation, nginx docs

W-01: Consolidate get_accessible_calendar_ids to single UNION query
instead of two separate DB round-trips.
W-02: Document that nginx rate limit on /api/events applies to all
methods (30r/m generous enough for GET polling at 2r/m).
W-03: Add weekly rule validation for consistency with other rule types.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/schemas/calendar_event.py

@@ -22,6 +22,8 @@ class RecurrenceRule(BaseModel):
         """Enforce required fields per rule type."""
         if self.type == "every_n_days" and self.interval is None:
             raise ValueError("every_n_days rule requires 'interval'")
+        if self.type == "weekly" and self.weekday is None:
+            raise ValueError("weekly rule requires 'weekday'")
         if self.type == "monthly_nth_weekday":
             if self.week is None or self.weekday is None:
                 raise ValueError("monthly_nth_weekday rule requires both 'week' and 'weekday'")

backend/app/services/calendar_sharing.py

@@ -22,14 +22,16 @@ LOCK_DURATION_MINUTES = 5
 
 async def get_accessible_calendar_ids(user_id: int, db: AsyncSession) -> list[int]:
     """Return all calendar IDs the user can access (owned + accepted shared memberships)."""
-    owned = await db.execute(select(Calendar.id).where(Calendar.user_id == user_id))
-    shared = await db.execute(
-        select(CalendarMember.calendar_id).where(
-            CalendarMember.user_id == user_id,
-            CalendarMember.status == "accepted",
+    result = await db.execute(
+        select(Calendar.id).where(Calendar.user_id == user_id)
+        .union(
+            select(CalendarMember.calendar_id).where(
+                CalendarMember.user_id == user_id,
+                CalendarMember.status == "accepted",
+            )
         )
     )
-    return [r[0] for r in owned.all()] + [r[0] for r in shared.all()]
+    return [r[0] for r in result.all()]
 
 
 async def get_user_permission(db: AsyncSession, calendar_id: int, user_id: int) -> str | None:

frontend/nginx.conf

@@ -124,7 +124,9 @@ server {
         include /etc/nginx/proxy-params.conf;
     }
 
-    # Event creation — rate-limited to prevent DB flooding via recurrence amplification
+    # Event creation — rate-limited to prevent DB flooding via recurrence amplification.
+    # Note: exact match applies to GET+POST; 30r/m with burst=10 is generous enough
+    # for polling (2r/m) and won't affect reads even with multiple tabs.
     location = /api/events {
         limit_req zone=event_create_limit burst=10 nodelay;
         limit_req_status 429;