feat: Mongo-backed Pods with full CRUD + member management

Pods are persisted in MongoDB and CRUD'd via /api/pods (list/create/get/
update/delete + add/remove member). Shared Pod reshaped to a persisted entity
(members: string[], description, timestamps) + PodInput. Backend seeds Demo/
Frontend/Backend Pods on first run (Squad -> Pod rename). Frontend replaces
hardcoded teams with live data: PodCard (member chips add/remove, inline edit,
delete, join) + CreatePodForm; App fetches+mutates via API. Removes teams.ts/
TeamCard; gitignores test artifacts.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/components/PodView.tsx

@@ -1,4 +1,4 @@
-import type { DemoTeam } from '../lib/teams.js';
+import type { Pod } from '@podman/shared';
 import { Avatar } from './Avatar.js';
 
 export function PodView({
@@ -7,7 +7,7 @@ export function PodView({
   devMode,
   onLeave,
 }: {
-  team: DemoTeam;
+  team: Pod;
   me: string;
   devMode: boolean;
   onLeave: () => void;