Report question: skip a broken card and tell the server

A generated matching card arrived on a phone with three identical
definitions (the generation guards now drop those), but there was no way
to get past a bad card from inside a session. The feed chrome (deck
study, review, mistakes and exam) now has the red "!" control: one tap
records the question, skips to the next card and shows an Undo toast.

- lib/question-reports.ts: the local list (freezmo.reports.v1, zod on
  read, capped 200) is the skip state — reported cards leave every
  session type, count as "not attempted" in the results instead of
  wrong, and Undo takes a report back. A deck where everything is
  reported stays studiable so it can be regenerated.
- POST /api/reports appends one JSON line per report to
  REPORTS_DIR/reports.jsonl (shared/freezmo/reports in production, the
  dev data dir in dev). Deliberately write-only: the question text is
  readable on the server (that is the point — prompt tuning) but never
  over HTTP, since the app has no auth. Best effort: offline reports stay
  local.
- The button: a red outlined rounded square with "!", the chrome's
  control size, in both feed headers (hidden on the results slide).
- config: REPORTS_DIR + RATE_LIMIT_REPORTS (20); the deploy creates the
  shared reports dir; the dev unit and AGENTS.md note the new server
  data location.
- Suites: phase-1 (append + validation + no GET), phase-2 (button, toast,
  server POST, local copy, skip counter, hidden next session, Undo, exam
  pool). SW -> freezmo-v38.

deploy/freezmo-dev.service

@@ -30,6 +30,7 @@ Environment=NEXT_DIST_DIR=.next-dev
 Environment=NEXT_PUBLIC_FREEZMO_DEV=1
 Environment=SYNC_DIR=%h/freezmo/.freezmo-dev/sync
 Environment=PUSH_DIR=%h/freezmo/.freezmo-dev/push
+Environment=REPORTS_DIR=%h/freezmo/.freezmo-dev/reports
 Environment=PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
 ExecStart=/bin/node %h/freezmo/node_modules/next/dist/bin/next dev -H 0.0.0.0 -p 3217
 Restart=always