fix(docker): publish on loopback by default; make a mounted state dir writable

Closes #1964.

- README's Docker recipes dropped v1's `127.0.0.1:` prefix, so
  `-p 6274:6274` published the Inspector on every host interface. The
  container's `HOST=0.0.0.0` governs the container's interfaces, not the
  host's, so `DANGEROUSLY_BIND_ALL_INTERFACES` never covered this. Verified
  against a real container: from a LAN peer, `GET /` served the injected
  `MCP_INSPECTOR_API_TOKEN`, and that token then unlocked `/api/*` with no
  `Origin` header (server.ts:241 allows origin-less requests). Restore the
  prefix on both recipes, on the port-remap examples, and in the web README.

- Adding a server failed inside the container the moment you mounted a
  volume to keep it. Docker seeds a named volume's ownership from the
  image's directory at the mount point, and creates it `root:root` when
  that directory is absent — so the non-root `node` user got
  `EACCES ... open '/home/node/.mcp-inspector/mcp.json.tmp-*'`. Create the
  dir in the image, owned by `node`, and document the volume recipe (plus
  the bind-mount `--user` caveat) — without a volume the catalog lives in
  the writable layer and `--rm` throws it away.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SFXDQBEjvjCEBhmYkmw79a

clients/web/README.md

@@ -172,7 +172,7 @@ The guard blocks only the **wildcard** all-interfaces addresses. Binding a **spe
 
 - **Bind a specific address.** `HOST=192.168.1.50` (a LAN IP) or a public IP works directly: the default origin allow-list follows the bind host, so `allowedOrigins` becomes `http://<that-host>:PORT` and a browser hitting that address is accepted with no extra config. (The host is canonicalized the way a browser is — so `HOST=127.1` advertises `http://127.0.0.1:PORT`, an IPv6 bind host is bracketed as `http://[2001:db8::1]:PORT`, and the port is dropped when it's the http default `:80` — matching what the browser sends.)
 - **Behind TLS or a reverse proxy**, the browser's `Origin` becomes the public origin (e.g. `https://inspector.example.com`, often without a port), which won't match the auto-derived `http://<bind-host>:PORT`. Set `ALLOWED_ORIGINS` to the real public origin(s): `ALLOWED_ORIGINS=https://inspector.example.com`.
-- **Using the `0.0.0.0` wildcard** (opt-in via `DANGEROUSLY_BIND_ALL_INTERFACES=true`, as the Docker image does): a wildcard bind also serves loopback, so the default allow-list is the loopback trio plus the canonical wildcard origins (`http://0.0.0.0:PORT`, `http://[::]:PORT`), and **local access works out of the box** — `docker run -p 6274:6274` browsed at `http://localhost:6274` connects with no extra config. Reaching it at a **non-loopback** address (a LAN IP, a public hostname) still needs `ALLOWED_ORIGINS` — but since that **replaces** the default, keep the loopback forms in the list if you also browse locally: `ALLOWED_ORIGINS=http://localhost:PORT,http://127.0.0.1:PORT,http://192.168.1.50:PORT,https://inspector.example.com`.
+- **Using the `0.0.0.0` wildcard** (opt-in via `DANGEROUSLY_BIND_ALL_INTERFACES=true`, as the Docker image does): a wildcard bind also serves loopback, so the default allow-list is the loopback trio plus the canonical wildcard origins (`http://0.0.0.0:PORT`, `http://[::]:PORT`), and **local access works out of the box** — `docker run -p 127.0.0.1:6274:6274` browsed at `http://localhost:6274` connects with no extra config. Reaching it at a **non-loopback** address (a LAN IP, a public hostname) still needs `ALLOWED_ORIGINS` — but since that **replaces** the default, keep the loopback forms in the list if you also browse locally: `ALLOWED_ORIGINS=http://localhost:PORT,http://127.0.0.1:PORT,http://192.168.1.50:PORT,https://inspector.example.com`.
 
 The bind-host guard and the `ALLOWED_ORIGINS` allow-list apply to both the prod server and `--dev`. Note that in **`--dev`** the Vite dev server _additionally_ enforces its own `server.allowedHosts` Host-header check, whose default accepts loopback and IP-literal hosts. The host you **bind** is auto-allowed (Vite adds the resolved `server.host` — which this config sets from `HOST` — to the allow-list), so `HOST=<hostname>` works out of the box under `--dev` too. What needs an explicit `server.allowedHosts` entry is reaching the dev server at a **different** name than the one bound — e.g. a wildcard bind reached by hostname, or a reverse-proxy domain. For those, prefer the prod server (`mcp-inspector --web`) or add the host to `server.allowedHosts`.