Podcast mode: notes read aloud with a lyric-style word highlight

The third segment of the note-powered wizards (Study deck / Homework /
Podcast) takes the same intake - photos, documents, pasted text, the share
target - and turns it into a spoken episode.

- prompts: PODCAST_SYSTEM_PROMPT writes for the ear (plain prose, no markdown,
  no visual references), chaptered into 3-8 sections around a length target.
- /api/podcast mirrors /api/generate's plumbing (rate limit, model gate,
  provider keys, heartbeats, the 2x deadline, the optional vision pass).
- storage: frezmo.podcasts.v1, zod-validated, included in the backup and the
  encrypted sync payload; a new library tab lists episodes with listen /
  rename / delete-with-undo, and the wizard switch deep-links in.
- player: the transcript is word-wrapped spans and the word under the voice
  rides a lyric-style highlight that keeps itself centred. Two clocks: exact
  onboundary events where the browser reports them, a per-word length timer
  where it does not (iOS Safari); the first boundary retires the timer.
  Pause = cancel + re-speak from the word, which makes resume, chapter jumps
  and tap-any-word-to-seek the same operation; the position saves on pause,
  page-hide and unmount, so reopening resumes. Speed rebuilds the engine and
  keeps playing; the Aero soundtrack pauses itself when the voice starts; a
  browser with no voice gets an honest note and a readable transcript.
- the script sits on a glass pane (plain paragraphs over Aero's grass failed
  contrast; the scan now covers the player too).

tests/podcast-test.mjs (17th suite) stubs the model and the speech engine and
drives the highlight by hand: 26 checks. All suites green, contrast clean.
Version 0.7.3, SW v95.

app/podcast/page.tsx

@@ -0,0 +1,34 @@
+import { ApiKeyGate } from "@/components/ApiKeyGate";
+import { AppHeader } from "@/components/AppHeader";
+import { RouteTransition } from "@/components/RouteTransition";
+import { Sidebar, SidebarOffset } from "@/components/Sidebar";
+import { PodcastWizard } from "@/components/podcast/PodcastWizard";
+import { WizardModeSwitch } from "@/components/WizardModeSwitch";
+
+export const metadata = {
+  title: "New podcast",
+};
+
+/**
+ * Podcast mode's intake: the same notes as a deck, but the output is a spoken
+ * episode with a synced transcript (see components/podcast).
+ */
+export default function PodcastPage() {
+  return (
+    <ApiKeyGate>
+      <div className="flex min-h-dvh">
+        <Sidebar />
+        <SidebarOffset />
+        <main className="flex min-h-dvh min-w-0 flex-1 flex-col">
+          <AppHeader />
+          <div className="mx-auto w-full max-w-3xl flex-1 px-4 pb-tabbar lg:px-10 lg:pb-16 lg:pt-10">
+            <WizardModeSwitch mode="podcast" />
+            <RouteTransition>
+              <PodcastWizard />
+            </RouteTransition>
+          </div>
+        </main>
+      </div>
+    </ApiKeyGate>
+  );
+}