Infra: split dev and production (releases, services, deploy script)

- Production now runs from ~/freezmo-prod/current (release symlink) as a
  standalone server on :3207; releases are exported by scripts/deploy.sh,
  built and e2e-verified on a temp port, switched atomically, health-
  checked via the new /api/healthz (commit + build time) and rolled back
  automatically on failure. Last 5 releases kept; scripts/rollback.sh for
  manual rollback. Shared env + data live in ~/freezmo-prod/shared/ and
  are symlinked into every release (existing sync/push data migrated and
  verified identical).
- Dev runs from ~/freezmo via freezmo-dev.service: next dev on :3217
  (LAN only), its own build folder (.next-dev via NEXT_DIST_DIR), its own
  data (~/freezmo/.freezmo-dev), DEV badge, dev favicon/theme colour,
  "Freezmo Dev" PWA identity and never the production service worker.
- /api/healthz + the Settings Details version row (short commit + build
  time). output: standalone in next.config (next start still works).
- AGENTS.md documents the workflow rules: only dev updates during a task,
  temporary dirs/ports for test builds, and deploy-at-the-end as the only
  production path. README gains an Environments and deploy section.
- Fix found by the rehearsal: lib/dev-mode.ts must not be a client module
  (a server component importing a constant from a "use client" module
  gets a truthy proxy, which baked dev metadata into production builds).
- SW -> freezmo-v34.

tests/lib.mjs

@@ -17,6 +17,12 @@ import path from "node:path";
 
 export const BASE = process.env.FREEZMO_URL || "http://127.0.0.1:3207";
 export const REPO = path.resolve(new URL("..", import.meta.url).pathname);
+/**
+ * Where suites that spawn their own `next start` instances run from. Defaults
+ * to the repo the tests live in; scripts/deploy.sh points it at the release
+ * checkout so the pre-switch e2e run is hermetic.
+ */
+export const SPAWN_CWD = process.env.FREEZMO_SPAWN_CWD || REPO;
 
 /* ------------------------------------------------------------------ */
 /* Browser                                                             */
@@ -276,7 +282,7 @@ export async function waitForHttp(url, attempts = 60) {
  */
 export function spawnApp(port, env = {}) {
   const server = spawn("npx", ["next", "start", "-p", String(port), "-H", "127.0.0.1"], {
-    cwd: REPO,
+    cwd: SPAWN_CWD,
     env: { ...process.env, ...env },
     stdio: "ignore",
     detached: true,