Persist prayer data to a mounted Docker volume via Express API

Replaces localStorage with a JSON-file backend (server.js). Prayers are
stored in /data/prayers.json, which is mounted as a named Docker volume so
data survives container restarts and rebuilds. React fetches from /api/prayers.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DReRqHxSYuVfCzTzQGD9hZ

src/App.tsx

@@ -8,6 +8,7 @@ type Filter = 'active' | 'answered' | 'all';
 export default function App() {
   const {
     prayers,
+    loading,
     addPrayer,
     updateAnswer,
     markAnswered,
@@ -111,6 +112,8 @@ export default function App() {
         </button>
       </div>
 
+      {loading && <p className="loading">Loading prayers…</p>}
+
       <ul className="prayer-list">
         {filtered.length === 0 && (
           <li className="empty">