perf: optimize DB queries, SSE polling, and client rendering

- Fix resolveCollaborator N+1: replace full User table scan with findFirst
- Fix getAllUsersWithStats N+1: use groupBy instead of per-user count queries
- Cache getTeamMemberIdsForAdminTeams and isAdminOfUser with React.cache
- Increase SSE poll interval from 1s to 2s across all 5 subscribe routes
- Add cleanupOldEvents method to session-share-events for event table TTL
- Add React.memo to all card components (Swot, Motivator, Weather, WeeklyCheckIn, YearReview)
- Fix WeatherCard useEffect+setState lint error with idiomatic prop sync pattern
- Add optimizePackageImports for DnD libs and poweredByHeader:false in next.config
- Add inline theme script in layout.tsx to prevent dark mode FOUC
- Remove unused Next.js template SVGs from public/

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

src/app/api/motivators/[id]/subscribe/route.ts

@@ -77,7 +77,7 @@ export async function GET(request: Request, { params }: { params: Promise<{ id:
       // Connection might be closed
       clearInterval(pollInterval);
     }
-  }, 1000); // Poll every second
+  }, 2000); // Poll every 2 seconds
 
   // Cleanup on abort
   request.signal.addEventListener('abort', () => {

src/app/api/sessions/[id]/subscribe/route.ts

@@ -77,7 +77,7 @@ export async function GET(request: Request, { params }: { params: Promise<{ id:
       // Connection might be closed
       clearInterval(pollInterval);
     }
-  }, 1000); // Poll every second
+  }, 2000); // Poll every 2 seconds
 
   // Cleanup on abort
   request.signal.addEventListener('abort', () => {

src/app/api/weather/[id]/subscribe/route.ts

@@ -80,7 +80,7 @@ export async function GET(request: Request, { params }: { params: Promise<{ id:
       // Connection might be closed
       clearInterval(pollInterval);
     }
-  }, 1000); // Poll every second
+  }, 2000); // Poll every 2 seconds
 
   // Cleanup on abort
   request.signal.addEventListener('abort', () => {

src/app/api/weekly-checkin/[id]/subscribe/route.ts

@@ -80,7 +80,7 @@ export async function GET(request: Request, { params }: { params: Promise<{ id:
       // Connection might be closed
       clearInterval(pollInterval);
     }
-  }, 1000); // Poll every second
+  }, 2000); // Poll every 2 seconds
 
   // Cleanup on abort
   request.signal.addEventListener('abort', () => {

src/app/api/year-review/[id]/subscribe/route.ts

@@ -80,7 +80,7 @@ export async function GET(request: Request, { params }: { params: Promise<{ id:
       // Connection might be closed
       clearInterval(pollInterval);
     }
-  }, 1000); // Poll every second
+  }, 2000); // Poll every 2 seconds
 
   // Cleanup on abort
   request.signal.addEventListener('abort', () => {