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.

public/icons/dev-favicon.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64" role="img" aria-label="Freezmo Dev">
+  <rect width="64" height="64" rx="14" fill="#1c1917"/>
+  <path d="M32 9 53 21v22L32 55 11 43V21Z" fill="none" stroke="#f59e0b" stroke-width="5" stroke-linejoin="round"/>
+  <path d="M11 21l21 12 21-12M32 33v22" fill="none" stroke="#f59e0b" stroke-width="4" stroke-linejoin="round"/>
+  <path d="M22 40h6l2.4-6 3.2 10 2.2-5h6" fill="none" stroke="#fbbf24" stroke-width="2.4" stroke-linecap="round" stroke-linejoin="round"/>
+</svg>

public/icons/dev-icon.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" role="img" aria-label="Freezmo Dev">
+  <rect width="512" height="512" rx="112" fill="#1c1917"/>
+  <path d="M256 72 424 168v176L256 440 88 344V168Z" fill="none" stroke="#f59e0b" stroke-width="40" stroke-linejoin="round"/>
+  <path d="M88 168l168 96 168-96M256 264v176" fill="none" stroke="#f59e0b" stroke-width="32" stroke-linejoin="round"/>
+  <text x="256" y="316" text-anchor="middle" font-family="system-ui, sans-serif" font-size="96" font-weight="700" fill="#fbbf24">DEV</text>
+</svg>