fix(docker): let Provider Settings admit the host through the published port

Docker delivers the host's own browser to the container from the container
network's gateway, never from 127.0.0.1, so the loopback-only admission gate
answered every POWER UP request with 403 and no key could be saved. The README
and CHANGELOG claimed otherwise; both are corrected here.

- keySetupCore: GEV_KEY_SETUP_TRUSTED_PEERS, an exact-address list (no
  wildcards, prefixes or hostnames) admitted alongside loopback. Unset trusts
  nothing, and the sharing, Host, Origin, Content-Type and proxy-header checks
  all still apply to a listed address. Twelve assertions pin each refusal.
- scripts/docker-start.mjs: the container entry point, shaped after
  scripts/pinokio-start.mjs. It reads the default gateway from /proc/net/route,
  trusts exactly that address, and starts Vite. No gateway (--network none)
  trusts nothing. The pure helpers are unit-tested and a contract test pins the
  Dockerfile CMD and the loopback-only publish.
- Dockerfile: install git. `npm test` builds fixtures with `git init`, so the
  suite failed 71 tests inside the image and the README's claim that it runs in
  the container was wrong.
- SECURITY.md and .env.example document the setting and why it is safe only
  behind a 127.0.0.1 publish; README gains the Linux/NAS id note and .dockerignore
  drops macOS AppleDouble sidecars, both reported on the PR.

Verified in Docker on a clean build: saving a key from the panel writes the
bind-mounted .env (0600 in the container), it survives `compose down`/`up`, and
REMOVE comments it back out. A foreign Origin, a foreign Host, a proxy header
and a sibling container on the same network are each refused. `npm run doctor`,
`npm test` (5067 passed, 1 skipped, 0 failed) and `npm run build` are green
inside the container.

Reported-by: @jklaze
Co-Authored-By: Bogdan Petrut <[email protected]>
Co-Authored-By: Claude Opus 5 <[email protected]>

src/keySetupCore.test.mjs

@@ -258,6 +258,23 @@ test('the admission gate refuses every non-local shape, one assertion per refusa
   assert.equal(admitKeySetupRequest({ ...local, env: { PINOKIO_SHARE_LOCAL: '1' } }).ok, false, 'LAN sharing disables the surface');
   // A LAN peer reaching a wide-bound server.
   assert.equal(admitKeySetupRequest({ ...local, remoteAddress: '192.168.1.20' }).ok, false, 'non-loopback socket refused');
+  // A container publishes its port on the host's loopback, yet the host's own
+  // browser still arrives from the container network's gateway. Only an exact
+  // address the operator listed admits it, and nothing else is relaxed.
+  const trusted = { GEV_KEY_SETUP_TRUSTED_PEERS: ' 10.0.0.9 , 172.29.73.1 ' };
+  const gateway = { ...local, remoteAddress: '172.29.73.1' };
+  assert.equal(admitKeySetupRequest(gateway).ok, false, 'container gateway refused without the opt-in');
+  assert.equal(admitKeySetupRequest({ ...gateway, env: trusted }).ok, true, 'listed peer admitted');
+  assert.equal(admitKeySetupRequest({ ...gateway, remoteAddress: '::ffff:172.29.73.1', env: trusted }).ok, true, 'IPv4-mapped form of a listed peer admitted');
+  assert.equal(admitKeySetupRequest({ ...local, remoteAddress: '192.168.1.20', env: trusted }).ok, false, 'unlisted peer still refused');
+  assert.equal(admitKeySetupRequest({ ...gateway, env: { GEV_KEY_SETUP_TRUSTED_PEERS: '*' } }).ok, false, 'wildcards are not addresses');
+  assert.equal(admitKeySetupRequest({ ...gateway, env: { GEV_KEY_SETUP_TRUSTED_PEERS: '172.29.73.0/24' } }).ok, false, 'prefixes are not addresses');
+  assert.equal(admitKeySetupRequest({ ...gateway, env: { GEV_KEY_SETUP_TRUSTED_PEERS: '' } }).ok, false, 'an empty list trusts nothing');
+  assert.equal(admitKeySetupRequest({ ...gateway, env: { GEV_KEY_SETUP_TRUSTED_PEERS: ' , , ' } }).ok, false, 'blank entries trust nothing');
+  assert.equal(admitKeySetupRequest({ ...gateway, env: { ...trusted, PINOKIO_SHARE_LOCAL: '1' } }).ok, false, 'sharing still disables the surface for a listed peer');
+  assert.equal(admitKeySetupRequest({ ...gateway, env: trusted, hostHeader: 'abc.trycloudflare.com' }).ok, false, 'a listed peer still needs a local Host');
+  assert.equal(admitKeySetupRequest({ ...gateway, env: trusted, origin: 'https://evil.example' }).ok, false, 'a listed peer still needs the exact Origin');
+  assert.equal(admitKeySetupRequest({ ...gateway, env: trusted, proxyHeaders: { 'x-forwarded-for': '203.0.113.5' } }).ok, false, 'a listed peer still refuses proxied requests');
   // Tunnel and DNS-rebinding traffic carries a foreign Host over a loopback socket.
   assert.equal(admitKeySetupRequest({ ...local, hostHeader: 'abc.trycloudflare.com' }).ok, false, 'foreign Host refused');
   assert.equal(admitKeySetupRequest({ ...local, hostHeader: 'workstation.local:4173' }).ok, false, 'non-localhost hostnames refused');