fix(invite-claim): send publicKey + JSON error responses

The /join and OIDC accept pages were calling /api/register/complete without
the public key extracted from the WebAuthn attestation. storeCredential writes
a credentials row with a NOT NULL public_key column, so the request crashed
with an unhandled exception and Hono replied "Internal Server Error" as plain
text — the client JSON.parse choked on it.

- Extract credential.response.getPublicKey() on the client and include it in
  the completion payload (both /join and /oidc/accept flows).
- Add app.onError to return JSON 500s on /api/* routes so any future crashes
  produce parseable error bodies instead of cascading into confusing "Unexpected
  token 'I'" errors in the browser.

src/encryptid/server.ts

@@ -484,6 +484,18 @@ app.use('*', cors({
   credentials: true,
 }));
 
+// Return JSON for unhandled exceptions on JSON API routes so client-side
+// `await res.json()` doesn't choke on plain-text "Internal Server Error".
+app.onError((err, c) => {
+  const path = c.req.path;
+  console.error(`EncryptID: ${c.req.method} ${path} failed:`, err);
+  const wantsJson = path.startsWith('/api/') || (c.req.header('accept') || '').includes('application/json');
+  if (wantsJson) {
+    return c.json({ error: 'Internal server error', detail: err.message }, 500);
+  }
+  return c.text('Internal Server Error', 500);
+});
+
 // /api/internal/* is for service-to-service calls over the Docker network only.
 // Traefik adds X-Forwarded-For for any request arriving through the public edge
 // (CF tunnel, direct HTTPS). Direct container-to-container fetches do not set it.
@@ -6385,6 +6397,11 @@ function joinPage(token: string): string {
           .replace(/\\+/g, '-').replace(/\\//g, '_').replace(/=/g, '');
         const clientDataJSON = btoa(String.fromCharCode(...new Uint8Array(credential.response.clientDataJSON)))
           .replace(/\\+/g, '-').replace(/\\//g, '_').replace(/=/g, '');
+        const publicKeyBytes = credential.response.getPublicKey ? credential.response.getPublicKey() : null;
+        const publicKey = publicKeyBytes
+          ? btoa(String.fromCharCode(...new Uint8Array(publicKeyBytes)))
+              .replace(/\\+/g, '-').replace(/\\//g, '_').replace(/=/g, '')
+          : '';
 
         const completeRes = await fetch('/api/register/complete', {
           method: 'POST',
@@ -6396,6 +6413,7 @@ function joinPage(token: string): string {
             deviceName: detectDeviceName(),
             credential: {
               credentialId,
+              publicKey,
               attestationObject,
               clientDataJSON,
               transports: credential.response.getTransports ? credential.response.getTransports() : [],
@@ -6728,6 +6746,7 @@ function oidcAcceptPage(token: string): string {
         });
 
         showStatus('Completing registration...');
+        const publicKeyBytes = credential.response.getPublicKey ? credential.response.getPublicKey() : null;
         const completeRes = await fetch('/api/register/complete', {
           method: 'POST',
           headers: { 'Content-Type': 'application/json' },
@@ -6738,6 +6757,7 @@ function oidcAcceptPage(token: string): string {
             deviceName: detectDeviceName(),
             credential: {
               credentialId: toB64url(credential.rawId),
+              publicKey: publicKeyBytes ? toB64url(publicKeyBytes) : '',
               attestationObject: toB64url(credential.response.attestationObject),
               clientDataJSON: toB64url(credential.response.clientDataJSON),
               transports: credential.response.getTransports ? credential.response.getTransports() : [],