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.

components/Sidebar.tsx

@@ -20,6 +20,7 @@ import {
 import { useTheme } from "@/components/ThemeToggle";
 import { createFolder, folderStore } from "@/lib/folders";
 import { haptic } from "@/lib/haptics";
+import { IS_DEV_INSTANCE } from "@/lib/dev-mode";
 import { useI18n } from "@/lib/i18n";
 import { ALL_FOLDERS, folderSelection, useSelectedFolder } from "@/lib/nav";
 import { UNORGANIZED_ID } from "@/lib/schemas";
@@ -102,7 +103,14 @@ function NavContent({ collapsed = false }: { collapsed?: boolean }) {
             className="size-7 shrink-0 rounded-lg shadow-[0_1px_3px_rgb(14_21_40/0.35)]"
           />
           {!collapsed ? (
-            <span className="text-[15px] font-semibold tracking-[-0.01em] text-[var(--text)]">Freezmo</span>
+            <>
+              <span className="text-[15px] font-semibold tracking-[-0.01em] text-[var(--text)]">Freezmo</span>
+              {IS_DEV_INSTANCE ? (
+                <span className="rounded-md border border-amber-400/60 bg-amber-400/15 px-1.5 py-0.5 text-[10px] font-bold uppercase tracking-wide text-amber-700 dark:text-amber-300">
+                  DEV
+                </span>
+              ) : null}
+            </>
           ) : null}
         </Link>
         {!collapsed ? (