--lan key persists across restarts; stale tabs get a readable 403

The key rotated on every server restart, stranding every phone that
held the previous cookie — during active development that guaranteed a
wall of refusals from stale polling tabs after each restart. The key
now lives in data/.lan_key (gitignored, 0600 — the Playwright-state
treatment for credential-adjacent files) and is reused across
restarts; delete the file to rotate. A keyless browser navigation now
gets a one-line HTML page saying what to do instead of raw JSON.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016jXZFSTZQKzAC8fqpWSz9g

data/title_edits.json

@@ -47,5 +47,10 @@
       "IMG_4502.jpeg"
     ],
     "confidence": "high"
+  },
+  {
+    "match": "ACTION CASTLE",
+    "title_raw": "Parsely",
+    "confidence": "high"
   }
 ]