feat: unified gateway route table (static · proxy · remote)

The gateway does two things — reverse-proxy services and serve static
frontends — but the dashboard/API route table only ever showed the proxy
routes, so 'serving a frontend' and 'proxying a service' looked like unrelated
features and castle-app/power-graph-app were invisible in the route view.

Now there's one concept: a route maps an address (path '/foo' or host 'foo.lan')
to a target of one kind — static (a built dist served by file_server), proxy
(a local service port), or remote (a service on another node).

- core: caddyfile.py gains compute_routes() — the single source of truth for
  the route list; generate_caddyfile_from_registry renders it (output byte-for-
  byte identical, verified against the live Caddyfile). Adds a GatewayRoute
  dataclass.
- api: GatewayRoute model → {address, kind, target, name, node}; GET /gateway
  builds from compute_routes (incl. config for static frontends + mesh for
  remote), so the table matches what Caddy actually does.
- app: Gateway panel shows Address · Kind · Target for every route (static
  frontends + host routes now appear); program detail shows 'Reachable at
  /foo/ · served (static)' for static frontends.
- cli: 'castle gateway status' prints the full route table.
- docs: registry.md/design.md/CLAUDE.md describe routes as one concept with
  three target kinds.

core 94 / cli 24 / api 52 green; ruff + app build clean; Caddyfile unchanged.

CLAUDE.md

@@ -128,8 +128,12 @@ code, artifacts, secrets; default `~/.castle`) and `CASTLE_DATA_DIR` (program
 data I/O on a dedicated volume; default `/data/castle`). Paths below use
 `$CASTLE_HOME` and `$CASTLE_DATA_DIR` accordingly.
 
-- **Gateway**: Caddy reverse proxy at port 9000, config generated from `castle.yaml`
-  into `$CASTLE_HOME/artifacts/specs/Caddyfile`. Dashboard served at root.
+- **Gateway**: Caddy at port 9000 — both a reverse proxy (to local/remote
+  services) and a static file server (for built frontends, served in place from
+  `<source>/<dist>`). Config generated from `castle.yaml` into
+  `$CASTLE_HOME/artifacts/specs/Caddyfile`. A route maps an address (path or
+  host) to a target of kind static/proxy/remote; `castle gateway status` lists
+  them. Dashboard (castle-app) served at root.
 - **Systemd**: User units generated under `~/.config/systemd/user/castle-*.service`.
   Use drop-in overrides (`*.service.d/*.conf`) for extra env vars that `castle deploy`
   shouldn't overwrite (e.g., `CASTLE_API_MQTT_ENABLED`).
@@ -165,7 +169,7 @@ Config:
 - `POST /apply` — Apply registry changes; `POST /deploy` — Deploy to runtime
 
 Gateway:
-- `GET /gateway` — Gateway info with route table and hostname
+- `GET /gateway` — Gateway info + full route table (every route tagged kind=static|proxy|remote, with its address and target)
 - `GET /gateway/caddyfile` — Generated Caddyfile content
 - `POST /gateway/reload` — Regenerate Caddyfile and reload Caddy