Add i18n, branding, user management, health checks, and cleanup for deployment

- Multi-language support (EN/DE) with i18n engine and language files
- Configurable branding (name, subtitle, logo) in Settings
- Global default language and per-user language preference
- User management router with CRUD endpoints
- Customer status sync on start/stop/restart
- Health check fixes: derive status from container state, remove broken wget healthcheck
- Caddy reverse proxy and dashboard env templates for customer stacks
- Updated README with real hardware specs, prerequisites, and new features
- Removed .claude settings (JWT tokens) and build artifacts from tracking
- Updated .gitignore for .claude/ and Windows artifacts

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

app/utils/security.py

@@ -89,3 +89,16 @@ def generate_relay_secret() -> str:
         A 32-character hex string.
     """
     return secrets.token_hex(16)
+
+
+def generate_datastore_encryption_key() -> str:
+    """Generate a base64-encoded 32-byte key for NetBird DataStoreEncryptionKey.
+
+    NetBird management (Go) expects standard base64 decoding to exactly 32 bytes.
+
+    Returns:
+        A standard base64-encoded string representing 32 random bytes.
+    """
+    import base64
+
+    return base64.b64encode(secrets.token_bytes(32)).decode()