Add image cropping to avatar upload and show avatars platform-wide

- Add react-easy-crop for circular crop + zoom UI on avatar upload
- Create server-side getUserAvatarUrl utility for generating pre-signed URLs
- Update all nav components (admin, jury, mentor, observer) to show user avatars
- Add avatar URLs to user list, mentor list, and project detail API responses
- Replace initials-only avatars with UserAvatar component across admin pages

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

src/server/routers/assignment.ts

@@ -1,6 +1,7 @@
 import { z } from 'zod'
 import { TRPCError } from '@trpc/server'
 import { router, protectedProcedure, adminProcedure } from '../trpc'
+import { getUserAvatarUrl } from '../utils/avatar-url'
 import {
   generateAIAssignments,
   generateFallbackAssignments,
@@ -31,14 +32,25 @@ export const assignmentRouter = router({
   listByProject: adminProcedure
     .input(z.object({ projectId: z.string() }))
     .query(async ({ ctx, input }) => {
-      return ctx.prisma.assignment.findMany({
+      const assignments = await ctx.prisma.assignment.findMany({
         where: { projectId: input.projectId },
         include: {
-          user: { select: { id: true, name: true, email: true, expertiseTags: true } },
+          user: { select: { id: true, name: true, email: true, expertiseTags: true, profileImageKey: true, profileImageProvider: true } },
           evaluation: { select: { status: true, submittedAt: true, globalScore: true, binaryDecision: true } },
         },
         orderBy: { createdAt: 'desc' },
       })
+
+      // Attach avatar URLs
+      return Promise.all(
+        assignments.map(async (a) => ({
+          ...a,
+          user: {
+            ...a.user,
+            avatarUrl: await getUserAvatarUrl(a.user.profileImageKey, a.user.profileImageProvider),
+          },
+        }))
+      )
     }),
 
   /**