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/components/swot/SwotCard.tsx

@@ -1,6 +1,6 @@
 'use client';
 
-import { forwardRef, useState, useTransition } from 'react';
+import { forwardRef, memo, useState, useTransition } from 'react';
 import type { SwotItem, SwotCategory } from '@prisma/client';
 import { updateSwotItem, deleteSwotItem, duplicateSwotItem } from '@/actions/swot';
 
@@ -21,7 +21,7 @@ const categoryStyles: Record<SwotCategory, { ring: string; text: string }> = {
   THREAT: { ring: 'ring-threat', text: 'text-threat' },
 };
 
-export const SwotCard = forwardRef<HTMLDivElement, SwotCardProps>(
+export const SwotCard = memo(forwardRef<HTMLDivElement, SwotCardProps>(
   (
     { item, sessionId, isSelected, isHighlighted, isDragging, linkMode, onSelect, ...props },
     ref
@@ -196,6 +196,5 @@ export const SwotCard = forwardRef<HTMLDivElement, SwotCardProps>(
       </div>
     );
   }
-);
-
+));
 SwotCard.displayName = 'SwotCard';