Add app update detection and multi-folder project support

Feature 1 - Update Detection: Query Gitea releases API on startup (3s
delay) and every 24h, compare patch versions by platform, show pulsing
"Update" button in TopBar with dialog for release notes/downloads.
Settings: auto-check toggle, manual check, dismiss per-version.

Feature 2 - Multi-Folder Projects: Replace single `path` with
`paths: Vec<ProjectPath>` (host_path + mount_name). Each folder mounts
to `/workspace/{mount_name}`. Auto-migrate old single-path JSON on load.
Container recreation via paths-fingerprint label. AddProjectDialog and
ProjectCard support add/remove/edit of multiple folders.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src/hooks/useProjects.ts

@@ -2,6 +2,7 @@ import { useCallback } from "react";
 import { useShallow } from "zustand/react/shallow";
 import { useAppState } from "../store/appState";
 import * as commands from "../lib/tauri-commands";
+import type { ProjectPath } from "../lib/types";
 
 export function useProjects() {
   const {
@@ -30,8 +31,8 @@ export function useProjects() {
   }, [setProjects]);
 
   const add = useCallback(
-    async (name: string, path: string) => {
-      const project = await commands.addProject(name, path);
+    async (name: string, paths: ProjectPath[]) => {
+      const project = await commands.addProject(name, paths);
       // Refresh from backend to avoid stale closure issues
       const list = await commands.listProjects();
       setProjects(list);