extract speech-to-text into its own plugin

Moves platform STT out into a plugin that owns the whole whisper.cpp contract: sidecar,
config (a JSON file under DATA_PATH/transcribe/, validated against the server before
storing), a thin proxy router, a skill so an agent knows the contract without being told,
and a script-mode file-browser task (not agentic — no model turn per audio file).

sidecar/transcribe.ts and its test moved unchanged from src/servers/api/stt/ — every
constant in it has a reason attached and none of it was touched.

The platform-side removal (routes, dead useAudioRecording path, Settings screen, locale
keys) lands in a separate, uncommitted change in the platform repo for review.

Not yet reachable from the file browser: the platform does not load tasks from a plugin's
directory yet (skills/affordances/notifications do). Ships anyway per instructions.

Officer-Session: 656f5c85-e49a-4f1f-b9f3-042a04b4d043

manifest.ts

@@ -0,0 +1,51 @@
+import type { PluginManifest } from '@@/plugins/manifest';
+
+/**
+ * Transcribe — Officer's speech-to-text, talking to a self-hosted whisper.cpp server.
+ *
+ * ── What this plugin is, and what it is not ──
+ *
+ * It does NOT run Whisper, and it does not ship a model. You point it at a whisper.cpp `/inference`
+ * server you already run (the same container the platform used to talk to directly) and it forwards to
+ * it. Nothing is transcribed here — the sidecar's whole job is the request shape: detect the language,
+ * then transcribe faithfully in it, tuned for one person talking into a phone.
+ *
+ * Named for the feature, not the implementation — the same reasoning as `photos` not `immich`. Swapping
+ * the backend for a different `/inference`-compatible server would not move the mount point or the route
+ * shape.
+ *
+ * ── Where the connection lives ──
+ *
+ * A single URL, in a JSON file under `DATA_PATH/transcribe/`, not in Postgres and not in this
+ * repository. There is only ever one Whisper server for the whole install — unlike `photos_config` or
+ * `jellyfin_servers`, nobody has a reason to keep more than one — so a file the owner can also edit by
+ * hand is simpler than a table with one row. See `sidecar/config.ts`.
+ *
+ * ── No `osDependencies` ──
+ *
+ * Nothing shells out. The sidecar reaches whisper.cpp with `fetch`, the same as the code it replaces did.
+ *
+ * ── No `web/` ──
+ *
+ * This plugin ships no dashboard route and no dock tile — `plugin.web` gates the tile, and a
+ * backend-only plugin has nothing to pin one to. It is reached from a task's right-click menu and by an
+ * agent that has read its skill, not by a screen.
+ */
+export const manifest: PluginManifest = {
+  publisher: 'officerdev',
+  version: '1.0.0',
+  platform: '>=1.0.0',
+
+  label: 'Transcribe',
+  summary: 'Speech-to-text over your own whisper.cpp server',
+  icon: 'AudioLines',
+  color: '#f97316',
+
+  permissions: [
+    {
+      key: 'transcribe',
+      label: 'Transcribe',
+      description: 'Turn audio into text over your own whisper.cpp server',
+    },
+  ],
+};