chore: backend fixes + vite config + AppShell cleanup

- pyproject.toml: add httpx>=0.27.0 dependency.
- frontend/vite.config.js: bind port to 31400, strictPort, proxy /api -> 31401.
- start.sh: rewrite as detached daemon (nohup + disown + PID files);
  re-running is treated as restart.
- .gitignore: ignore .run/ (PID files).
- frontend AppShell.vue: drop unused GitHub Star link.

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

frontend/vite.config.js

@@ -4,10 +4,11 @@ import vue from '@vitejs/plugin-vue'
 export default defineConfig({
   plugins: [vue()],
   server: {
-    port: 3000,
+    port: 31400,
+    strictPort: true,
     proxy: {
       '/api': {
-        target: 'http://localhost:8000',
+        target: 'http://localhost:31401',
         changeOrigin: true,
       },
     },