Release Subpipe r21 and LuCI r24

[damocjwj]

What changed

• update the core package to 0.7.0-r21 and LuCI/i18n packages to 0.7.0-r24
• remove duplicate post-install and uci-defaults service starts
• allow procd recovery when a configured interface address is not available yet, while retaining permanent bind validation
• classify normal service messages as informational and restrict the LuCI log view to the exact subpipe: tag
• replace private modal-overlay hooks with native LuCI notifications and modal actions
• retain native semantic status labels, remove duplicate page headings, and synchronize Simplified Chinese translations
• add standalone architecture and operations guides, expand the root and package references, and strengthen repository checks

Why

The standalone feed lagged behind the implementation already validated on a real OpenWrt device. In particular, installation could trigger the service multiple times, an interface address assigned late during boot could prevent procd registration, and LuCI relied on private modal DOM details. This release synchronizes the tested implementation and documents its operational and security boundaries.

Impact

The UCI schema and public CLI/RPC interfaces remain compatible with the existing 0.7.0-r17+ layout. Normal package upgrades preserve /etc/config/subpipe. Older pre-r17 configurations still require manual recreation. The service remains disabled by default.

Validation

• gofmt, go vet ./..., and go test -race ./...
• JavaScript syntax and LuCI UI regression tests
• Lua syntax, JSON, POT/PO and source-manifest checks
• clean OpenWrt cross-build of subpipe, luci-app-subpipe, and luci-i18n-subpipe-zh-cn
• real-device validation of procd start/stop/restart, HTTP health, RPC, Lua module behavior, transient-address/permanent-port preflight behavior, log priority/filtering, and unchanged UCI configuration hash