mobile: network member management and avatars (parity phase 2)

- New NetworkSettingsScreen (reachable from the stream-list header) lists
  members with admin remove, an invite-by-email sheet, and pending
  invitations with revoke — backed by new use-member-management hooks.
- Avatars: add avatar_object_id to HumanSchema, uploadAvatar/deleteAvatar/
  getAvatarDownloadUrl client methods (raw PUT via expo-file-system), a
  use-avatar-url hook, and image rendering in the shared Avatar component.
  AccountScreen gains a tap-to-change profile picture via expo-image-picker.
- auth-store gains refreshUser to pick up avatar changes.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01LqGPzXQ1AA9CqYHgCgmbtV

js/mobile/app.config.ts

@@ -55,6 +55,13 @@ const config: ExpoConfig = {
           'Flowy uses your microphone to record voice messages.',
       },
     ],
+    [
+      'expo-image-picker',
+      {
+        photosPermission:
+          'Flowy uses your photo library to set your profile picture.',
+      },
+    ],
     [
       'expo-notifications',
       {