Older Caddy versions don't support `list-modules --json`, which made the
plugins page fail with an opaque "exit status 1". Surface stderr in the error
and fall back to parsing the plain-text output (--packages / --skip-standard)
when --json is unsupported, so module detection works on any Caddy version.
Add unit/integration tests across backend handlers, auth, caddy and
util packages, plus frontend component and API tests with the new
test setup. Update CI workflow and Vite config to run the suites.
Introduce per-host plugin support: Caddy module discovery, module
config endpoints, plugin schemas (basicauth, cloudflare) and the
host plugins API. On the frontend, add the Plugins page, plugin/host
plugin dialogs and schema-driven form fields.
Introduce a Provider interface selectable via CPM_CADDY_MODE:
- CaddyfileProvider renders per-host snippets (template whitespace fixed)
- APIProvider manages Caddy's JSON config via the admin API
Add configurable reload strategy (systemd/exec/api/none) and a
configurable listen address for the bootstrapped server in API mode.
Includes unit tests for the JSON builder, provider factory and the
API provider (httptest).
