email, extracted from the officer platform

IMAP and Gmail sync into a per-account SQLite store, with the mail read and
composed in the browser.

moved whole from src/servers/sidecar/email (14 files), src/servers/api/email,
officer_db/src/email, and the Screens/Dashboard/Email tree. what changed on the
way out:

- credentials are encrypted. the column was plaintext jsonb holding an IMAP app
  password that the SMTP transport read straight out of the row; it is now
  AES-256-GCM under this plugin's own 'email' secret-store purpose, sealed and
  opened in queries.ts alone so nothing above it can hold ciphertext by
  accident. no plaintext fallback on read - a value that does not verify is an
  error.
- the router derives its prefix from mountPrefix() instead of the literal
  '/api/email', which was only correct for a first-party publisher.
- the frontend became panels.ts + layout.ts. the two panel appTypes that were
  null are now declared, because the platform screen used to override them by
  panel id and a plugin has no such hook.
- account management became a modal. it was a section in the platform's
  Settings, which a plugin cannot contribute to, and a panel does not work
  either: PluginScreen renders the workspace locked, so a panel outside the
  default layout is unreachable. it follows Compose, which had already solved
  this.
- 17 palette classes replaced with semantic tokens.

not verified: this has never run. it was switched off in the platform on
2026-08-13 and its table was never created, so nothing has exercised sync,
sending or the UI since. the first install is the first test.

web/shared.ts

@@ -0,0 +1,13 @@
+import { useParams } from 'react-router';
+
+// Which email is open is `/email/:emailId`. The route pair already existed, but the URL was a mirror
+// rather than the state: the selection lived in an `EMAIL_SELECTED` global and two effects copied it
+// back and forth with the route. That round-trip is what kept a row a `<button>` — nothing to link to,
+// no cmd-click, no middle-click — and it meant Back raced the effect that had just written the URL
+// with `replace`. The param is the state now; there is nothing to keep in sync.
+
+/** `search` carries the folder you are reading in (`?folder=sent`), which a bare pathname would drop. */
+export const emailPath = (id: string, search = '') => `/email/${encodeURIComponent(id)}${search}`;
+
+/** The open email, or null on the bare `/email` route — which is a real state, not one to redirect away. */
+export const useSelectedEmailId = (): string | null => useParams<{ emailId?: string }>().emailId ?? null;