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>

package-lock.json

@@ -62,6 +62,7 @@
         "papaparse": "^5.4.1",
         "react": "^19.0.0",
         "react-dom": "^19.0.0",
+        "react-easy-crop": "^5.5.6",
         "react-hook-form": "^7.54.2",
         "react-leaflet": "^5.0.0",
         "react-phone-number-input": "^3.4.14",
@@ -10637,6 +10638,12 @@
         "node": ">=6.0.0"
       }
     },
+    "node_modules/normalize-wheel": {
+      "version": "1.0.1",
+      "resolved": "https://registry.npmjs.org/normalize-wheel/-/normalize-wheel-1.0.1.tgz",
+      "integrity": "sha512-1OnlAPZ3zgrk8B91HyRj+eVv+kS5u+Z0SCsak6Xil/kmgEia50ga7zfkumayonZrImffAxPU/5WcyGhzetHNPA==",
+      "license": "BSD-3-Clause"
+    },
     "node_modules/nypm": {
       "version": "0.6.4",
       "resolved": "https://registry.npmjs.org/nypm/-/nypm-0.6.4.tgz",
@@ -11643,6 +11650,20 @@
         "react": "^19.2.4"
       }
     },
+    "node_modules/react-easy-crop": {
+      "version": "5.5.6",
+      "resolved": "https://registry.npmjs.org/react-easy-crop/-/react-easy-crop-5.5.6.tgz",
+      "integrity": "sha512-Jw3/ozs8uXj3NpL511Suc4AHY+mLRO23rUgipXvNYKqezcFSYHxe4QXibBymkOoY6oOtLVMPO2HNPRHYvMPyTw==",
+      "license": "MIT",
+      "dependencies": {
+        "normalize-wheel": "^1.0.1",
+        "tslib": "^2.0.1"
+      },
+      "peerDependencies": {
+        "react": ">=16.4.0",
+        "react-dom": ">=16.4.0"
+      }
+    },
     "node_modules/react-hook-form": {
       "version": "7.71.1",
       "resolved": "https://registry.npmjs.org/react-hook-form/-/react-hook-form-7.71.1.tgz",