Make every identity editable: agent and operator names plus avatars

- Migration 049: avatar_emoji/avatar_color on agents and employees
- updateAgent accepts a new name (mention-name validated) and avatar;
  new updateEmployeeProfile renames the operator and sets their avatar
- Avatars are emoji-on-color tiles (renderer CSP blocks remote images);
  an AvatarDirectoryContext built from the snapshot lets the shared
  Avatar component honor custom looks at every call site - chat rows,
  conversation list, org chart, office card, sidebar - without
  threading props through pages
- Team edit dialog gains Name + avatar editor (CEO included); the
  sidebar foot opens an Edit-profile dialog for the operator
- e2e: rename an agent to a new mention handle with an emoji avatar,
  edit the operator profile, both verified in the live shell

src/shared/domain.ts

@@ -49,6 +49,8 @@ export interface EmployeeRecord {
   orgId: string;
   displayName: string;
   role: string;
+  avatarEmoji: string | null;
+  avatarColor: string | null;
   createdAt: string;
 }
 
@@ -69,6 +71,8 @@ export interface AgentRecord {
   heartbeatEnabled: boolean;
   heartbeatIntervalSec: number;
   lifecycle: string;
+  avatarEmoji: string | null;
+  avatarColor: string | null;
   createdAt: string;
 }