perf(quick-wins): batch collaborator resolution, debounce SSE refresh, loading states

- Eliminate N+1 on resolveCollaborator: add batchResolveCollaborators() in
  auth.ts (2 DB queries max regardless of session count), update all 4
  workshop services to use post-batch mapping
- Debounce router.refresh() in useLive.ts (300ms) to group simultaneous
  SSE events and avoid cascade re-renders
- Call cleanupOldEvents fire-and-forget in createEvent to purge old SSE
  events inline without blocking the response
- Add loading.tsx skeletons on /sessions and /users matching actual page
  layout (PageHeader + content structure)
- Lazy-load ShareModal via next/dynamic in BaseSessionLiveWrapper to reduce
  initial JS bundle

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

src/services/moving-motivators.ts

@@ -1,5 +1,5 @@
 import { prisma } from '@/services/database';
-import { resolveCollaborator } from '@/services/auth';
+import { resolveCollaborator, batchResolveCollaborators } from '@/services/auth';
 import { getTeamMemberIdsForAdminTeams } from '@/services/teams';
 import { createSessionPermissionChecks } from '@/services/session-permissions';
 import { createShareAndEventHandlers } from '@/services/session-share-events';
@@ -21,7 +21,7 @@ const motivatorInclude = {
 // ============================================
 
 export async function getMotivatorSessionsByUserId(userId: string) {
-  return mergeSessionsByUserId(
+  const sessions = await mergeSessionsByUserId(
     (uid) =>
       prisma.movingMotivatorsSession.findMany({
         where: { userId: uid },
@@ -33,14 +33,18 @@ export async function getMotivatorSessionsByUserId(userId: string) {
         where: { userId: uid },
         include: { session: { include: motivatorInclude } },
       }),
-    userId,
-    (s) => resolveCollaborator(s.participant).then((r) => ({ resolvedParticipant: r }))
+    userId
   );
+  const resolved = await batchResolveCollaborators(sessions.map((s) => s.participant));
+  return sessions.map((s) => ({
+    ...s,
+    resolvedParticipant: resolved.get(s.participant.trim()) ?? { raw: s.participant, matchedUser: null },
+  }));
 }
 
 /** Sessions owned by team members (where user is team admin) that are NOT shared with the user. */
 export async function getTeamCollaboratorSessionsForAdmin(userId: string) {
-  return fetchTeamCollaboratorSessions(
+  const sessions = await fetchTeamCollaboratorSessions(
     (teamMemberIds, uid) =>
       prisma.movingMotivatorsSession.findMany({
         where: { userId: { in: teamMemberIds }, shares: { none: { userId: uid } } },
@@ -48,9 +52,13 @@ export async function getTeamCollaboratorSessionsForAdmin(userId: string) {
         orderBy: { updatedAt: 'desc' },
       }),
     getTeamMemberIdsForAdminTeams,
-    userId,
-    (s) => resolveCollaborator(s.participant).then((r) => ({ resolvedParticipant: r }))
+    userId
   );
+  const resolved = await batchResolveCollaborators(sessions.map((s) => s.participant));
+  return sessions.map((s) => ({
+    ...s,
+    resolvedParticipant: resolved.get(s.participant.trim()) ?? { raw: s.participant, matchedUser: null },
+  }));
 }
 
 const motivatorByIdInclude = {