fix(admin-security): close the bearer-cookie ride; require session for admin gate (0.87.10)

Two follow-ups to 0.87.2 + 0.87.3 from the adversarial review:

1. **CSRF cookie-ride.** Bearer-bypass branch checked Authorization
   header presence only — an attacker page could mint `Authorization:
   Bearer junk` and ride the still-attached session cookie. Bypass now
   requires bearer AND no cookie. Drive the cookie-name comparison off
   `SESSION_COOKIE_NAME` and split on `=` (not prefix).

2. **`require_can_edit` admin path open to bearer.** Now reads admin
   authority off an `Option<CurrentSessionUser>` extractor — None on
   bearer-only requests. Owner-match path still accepts bearer; admin
   path is cookie-gated.

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

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.87.9",
+  "version": "0.87.10",
   "private": true,
   "type": "module",
   "scripts": {