Observability + warming guardrails (Codex)

* client_error details, not just a count: new client_errors table + POST
  /api/client-error (reason/path/user-agent/time) + GET /api/admin/client-errors.
  The boot-seatbelt beacon now sends the reason + path (once per page); the admin
  Overview lists the recent errors so we can tell chunk vs SW vs API vs JS — the
  truth meter for the next day as the new SW propagates.
* Deploy warming now also hits the shell, routes (/play /account /admin), SW,
  version.json, word lists, and icons/logo/font — not just immutable chunks.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

goodnews/db.py

@@ -260,6 +260,15 @@ CREATE TABLE IF NOT EXISTS feedback_replies (
 );
 CREATE INDEX IF NOT EXISTS idx_feedback_replies_fid ON feedback_replies(feedback_id);
 
+CREATE TABLE IF NOT EXISTS client_errors (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    reason TEXT NOT NULL DEFAULT '',
+    path TEXT NOT NULL DEFAULT '',
+    user_agent TEXT NOT NULL DEFAULT '',
+    app_version TEXT NOT NULL DEFAULT '',
+    created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+
 CREATE TABLE IF NOT EXISTS word_pool (
     word TEXT NOT NULL,
     variant TEXT NOT NULL,       -- '5' | '6'