Security hardening: invited user onboarding flow (C1–N7)

- C1: verify.php now filters license='owner' — invite tokens no longer accepted
- C1: onboarding API rejects non-owner sessions
- C2: Existing-user invite requires explicit acceptance via accept_invite.php
- C2: New accept_invite.php page and API engine added
- C2: inviteUser() generates token + expiry for existing users; resendInvite() handles active users
- C3: session_regenerate_id(true) before writing invite session keys on both invite pages
- C4: invited_onboarding API wraps activation in transaction with SELECT FOR UPDATE; rowCount check added; SQLSTATE 23000 caught cleanly
- C5: inviteUser() and resendInvite() two-table writes wrapped in transactions
- M2: removeUser() wrapped in transaction with FOR UPDATE; clears default_company on active user removal
- M4: Logged-in user guard added to invited_onboarding.php and accept_invite.php
- M5: manage_users.php uses $server_url instead of HTTP_HOST for invite URLs
- M6: Username regex enforces 3-32 chars; reserved name blocklist added
- N5: searchUsers() changed from LIKE fuzzy search to exact email match only
- N7: resendInvite() rate-limited to once per 60s via invite_resent_at column
- Schema: company_map_user gains invite_expires_at and invite_resent_at columns

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

app/login/verify.php

@@ -15,10 +15,13 @@
     }
 
     // ── Look up token ─────────────────────────────────────────────
+    // license='owner' guard: invited users also have verify_token set, but they
+    // must use invited_onboarding.php — never this flow.
     $sth = $pdo1->prepare("
         SELECT user_id, name, status, verify_expires_at
         FROM user
         WHERE verify_token = :token
+          AND license      = 'owner'
         LIMIT 1
     ");
     $sth->execute([':token' => $token]);