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-cards.php

@@ -243,6 +243,14 @@ if (preg_match('#^/api/collab-cards/([a-zA-Z0-9_-]+)/([a-zA-Z0-9_-]+)$#', $route
 
 // ── Collab attachments (images/PDFs/audio referenced by collab cards) ─
 
+// Attachment filenames always follow the hyprcrd upload pattern
+// (bin2hex(random_bytes(16)).<ext>). Enforce server-side so malicious
+// clients can't poison the DB with traversal-shaped names that later
+// surface in UIs or get forwarded to filesystem APIs.
+function collabAttachmentFilenameValid(string $fn): bool {
+    return (bool)preg_match('/^[a-f0-9]{8,64}\.[a-z0-9]{1,8}$/', $fn);
+}
+
 if ($route === '/api/collab-attachments' && $method === 'POST') {
     if (!$clientTenant) jsonResponse(['error' => 'unauthorized'], 401);
     $input = json_decode(file_get_contents('php://input'), true) ?: [];
@@ -250,6 +258,7 @@ if ($route === '/api/collab-attachments' && $method === 'POST') {
     $filename = (string)($input['filename'] ?? '');
     $data = (string)($input['data'] ?? '');
     if (!$bucketUid || !$filename || !$data) jsonResponse(['error' => 'bucket_uid, filename, and data required'], 400);
+    if (!collabAttachmentFilenameValid($filename)) jsonResponse(['error' => 'invalid filename'], 400);
     if (!collabCardsIsMember($db, $bucketUid, (int)$clientTenant['id'])) {
         jsonResponse(['error' => 'not a member of this bucket'], 403);
     }
@@ -277,6 +286,7 @@ if ($route === '/api/collab-attachments' && $method === 'GET') {
     $bucketUid = trim($_GET['bucket_uid'] ?? '');
     $filename = trim($_GET['filename'] ?? '');
     if (!$bucketUid) jsonResponse(['error' => 'bucket_uid required'], 400);
+    if ($filename !== '' && !collabAttachmentFilenameValid($filename)) jsonResponse(['error' => 'invalid filename'], 400);
     if (!collabCardsIsMember($db, $bucketUid, (int)$clientTenant['id'])) {
         jsonResponse(['error' => 'not a member of this bucket'], 403);
     }