Show real photos for people instead of scene art

Your avatar is your photo, picked from the device by tapping it on Home or
from a new Profile photo row in Settings, shrunk to 256 px and kept on the
phone (there is no upload endpoint yet). Group members show the photo the
server sends in a new `photo` field, everywhere avatars appear. Without a
photo, an initial on a neutral disc. Mock mode bundles free Unsplash
portraits for the sample people.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KhQh614DMeYoQEH9SoMRUw

frontend/lib/Grounded/mock/MockMemory.dart

@@ -21,7 +21,8 @@ class MockMemory extends InternalMemory {
       _seeded = true;
       setMyDescription(
           MeDescription(id: "mock-user", name: "Alex", token: "mock-token"));
-      setUserDetails(UserDetails(pic: "", name: "Alex"));
+      setUserDetails(UserDetails(
+          pic: "asset:assets/images/person_alex.jpg", name: "Alex"));
       setTodos(<TodoItem>[
         TodoItem(id: "t1", title: "Pick up gym kit"),
         TodoItem(id: "t2", title: "Book physio for Thursday"),
@@ -51,8 +52,9 @@ class MockMemory extends InternalMemory {
         title: title,
         kind: kind,
         startedAt: at,
-        seconds: (seconds * (held ? 1 : 0.5) * (0.85 + random.nextDouble() * 0.3))
-            .round(),
+        seconds:
+            (seconds * (held ? 1 : 0.5) * (0.85 + random.nextDouble() * 0.3))
+                .round(),
         completedSteps: held ? steps : 1 + random.nextInt(steps - 1),
         totalSteps: steps,
       ));