security: v2.0 — AES-GCM crypto, SSRF guards, rate limits, hardening

Breaking wire-format change: dual-read (V1+V2) / single-write (V2) so
existing user secrets, stored messages, and inter-tenant key keep
working. Old clients and relays lose cross-version chat until both
sides are upgraded.

Relay
- Switch clientEncrypt/masterEncrypt to AES-256-GCM with HKDF-derived
  per-ciphertext salts; keep CBC-V1 fallback on decrypt only.
- On-bootstrap migration re-envelopes tenant secret_encrypted and the
  inter-tenant key to GCM-V2 (idempotent).
- CORS: stop reflecting arbitrary Origin; allow own origin + optional
  RELAY_CORS_ORIGINS env allowlist; drop Access-Control-Allow-Credentials.
- Generic error messages replace "no such user: <name>" enumeration.
- Exception messages no longer echoed back; logged server-side.
- Collab-lock max hold capped at 10min so a member can't grief-refresh
  forever.
- Attachment filenames validated against hex.<ext> pattern.
- Passwords min length 10; /api/account/password rate-limited.

App / Electron client
- Shared hyprcrdRelayEncrypt/Decrypt helpers (GCM-V2 write, V1 read).
- Chat + collab-buckets plugins delegate to the shared helpers.
- Poll + push + attachments migrated to the dual-format path.
- /api/relay/settings GET returns has_key boolean; secret never echoed.
- Setup endpoint now CSRF-checked.
- SSRF: CURLOPT_PROTOCOLS restricted to HTTP(S) everywhere; bookmarks
  favicon fetch also blocks private/loopback/link-local.
- Login / password-change rate limiter moved to DB-backed IP keying.
- Passwords min length 10 throughout.
- Zip import enforces per-file (25MB) and total (500MB) caps, extension
  allowlist, no-overwrite.
- Verbose relay-push debug gated behind APP_DEBUG env.

Version bumped to 2.0.0 (protocol-breaking).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

relay/inc/routes/collab-buckets.php

@@ -50,7 +50,8 @@ if ($route === '/api/collab-buckets' && $method === 'POST') {
         $db->commit();
     } catch (Throwable $e) {
         if ($db->inTransaction()) $db->rollBack();
-        jsonResponse(['error' => 'create failed: ' . $e->getMessage()], 500);
+        @error_log('[hyprcrd-relay] collab bucket create failed: ' . $e->getMessage());
+        jsonResponse(['error' => 'create failed'], 500);
     }
     jsonResponse(['ok' => true, 'uid' => $uid, 'members' => array_values($resolved)]);
 }
@@ -102,7 +103,7 @@ if (preg_match('#^/api/collab-buckets/([a-zA-Z0-9_-]+)$#', $route, $m) && $metho
         $newOwnerName = trim((string)$input['owner']);
         if ($newOwnerName === '') jsonResponse(['error' => 'owner cannot be empty'], 400);
         $newOwner = getTenantByUsername($db, $newOwnerName);
-        if (!$newOwner) jsonResponse(['error' => "no such user: $newOwnerName"], 404);
+        if (!$newOwner) jsonResponse(['error' => 'user not found'], 404);
         $memCheck = $db->prepare('SELECT 1 FROM collab_bucket_members WHERE bucket_uid = :b AND tenant_id = :t');
         $memCheck->execute(['b' => $uid, 't' => $newOwner['id']]);
         if (!$memCheck->fetchColumn()) {