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.

lib/config.ts

@@ -36,6 +36,7 @@ export type ServerConfig = {
     sync: number;
     push: number;
     chat: number;
+    reports: number;
   };
   sync: {
     /** Where opaque encrypted sync blobs live (SYNC_DIR). */
@@ -53,6 +54,10 @@ export type ServerConfig = {
     /** Where push subscriptions live (PUSH_DIR). */
     dir: string;
   };
+  reports: {
+    /** Where reported questions are appended, one JSON line each (REPORTS_DIR). */
+    dir: string;
+  };
 };
 
 /** What a single request should use to talk to Ollama. */
@@ -149,6 +154,8 @@ export function getServerConfig(): ServerConfig {
       push: positiveInt(process.env.RATE_LIMIT_PUSH, 30),
       // Chat turns are one model call each, but users send them in bursts.
       chat: positiveInt(process.env.RATE_LIMIT_CHAT, 60),
+      // Question reports are cheap file appends.
+      reports: positiveInt(process.env.RATE_LIMIT_REPORTS, 20),
     },
     sync: {
       dir: process.env.SYNC_DIR?.trim() || path.join(process.cwd(), ".freezmo", "sync"),
@@ -161,6 +168,9 @@ export function getServerConfig(): ServerConfig {
       subject: process.env.VAPID_SUBJECT?.trim() || "mailto:freezmo@localhost",
       dir: process.env.PUSH_DIR?.trim() || path.join(process.cwd(), ".freezmo", "push"),
     },
+    reports: {
+      dir: process.env.REPORTS_DIR?.trim() || path.join(process.cwd(), ".freezmo", "reports"),
+    },
   };
 }