refactor: daemon collectors, thin webui proxies, pure config reads

- move state collectors from lib/state.py to daemon/collectors/ (7
  modules, registration side-effect; daemon/server.py imports the
  package before the first populate())
- webui/api: new daemon_route() decorator factory in common.py
  collapses the try/except daemon-proxy boilerplate in all 8
  blueprints (rules/params/body/transform keep responses identical)
- firewall: interface-coverage invariant — config is the source of
  truth for zone interfaces (absent key = empty, no hands-off
  zones); pure validate_coverage() enforced at save (400) and apply
  (409, force: true overrides), top-level `unmanaged` exemption
- lib: get_config() reads are now pure (no dir creation or writes);
  new lib/bootstrap.py creates runtime dirs and persists the
  one-shot nginx legacy migration at daemon start, after
  system_import (lib.nginx.migrate_config_file)
- lib/common: compute_pending() apply-bookkeeping helper
- daemon: emit_and_refresh() handler helper; refresh_state(bump=) so
  /status/refresh no longer bumps versions (poll/mutation only)
- acme: move --log last so acme.sh never treats a real arg as the
  log-file argument
- docs: AGENTS.md, config.md, state-model.md, api.md updated;
  HARDEN.md dropped (plan implemented); apply-confirm force wording

Tests: 917 passed; ruff check + format clean.

daemon/collectors/__init__.py

@@ -0,0 +1,26 @@
+"""State collectors for vacuum-walld.
+
+Importing this package registers every collector with the ``lib.state``
+store (registration side effect). Import it before the first
+``populate()``/``poll()`` call.
+"""
+
+from daemon.collectors import (
+    acme,
+    dnsmasq,
+    firewall,
+    networkd,
+    nginx,
+    system,
+    wireguard,
+)
+
+__all__ = [
+    "acme",
+    "dnsmasq",
+    "firewall",
+    "networkd",
+    "nginx",
+    "system",
+    "wireguard",
+]