fix(db): quote SQLCipher PRAGMA hex key to fix fresh install crash

The hex-encoded encryption key (x'...') is not valid as a bare PRAGMA
value in better-sqlite3. Wrapping it in double quotes produces valid
SQLCipher PRAGMA syntax.

Fixes #3

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

server/db.js

@@ -33,7 +33,8 @@ function init() {
 
   if (DB_KEY) {
     // Nur wirksam wenn Binary gegen SQLCipher kompiliert ist (Docker)
-    db.pragma(`key=x'${Buffer.from(DB_KEY, 'utf8').toString('hex')}'`);
+    db.pragma(`key="x'${Buffer.from(DB_KEY, 'utf8').toString('hex')}'"`);
+
     // Sicherstellen dass die Datenbank tatsächlich entschlüsselbar ist
     try {
       db.prepare('SELECT count(*) FROM sqlite_master').get();