feat: gsc-shell-api v0.1 — central chrome data API

Tiny Go service that returns ShellConfig JSON for any registered app.
Backs the runtime-loaded <AppShell> component being added to
@limitless/ui (next).

Endpoints:
  GET /api/v1/shell/{appKey}  → app + branding + user + menus, ETag-cached
  GET /api/v1/apps            → registered app inventory
  GET /healthz, /readyz       → ops probes

Auth:
  Keycloak Bearer JWT validated against the gosecCloud realm.
  Discovery URL is overridable so pods can hit Keycloak via the
  in-cluster service (https://keycloak.keycloak.svc.cluster.local:8443)
  while still validating the canonical issuer (auth.gosec.cloud).
  Lazy JWKS init — pod stays up if Keycloak is briefly unreachable.

Data model (gsc_core.shell):
  apps · menu_items (zone enum: topbar/sidebar/footer/user-menu) ·
  menu_role_grants (Keycloak realm roles, OR semantics, empty=all) ·
  branding

Seed includes the 8 gsc-crm sidebar items + topbar search +
user-menu (settings/support/logout) + footer (docs).

K8s:
  Namespace gsc-shell (ambient mesh).
  Deployment 2 replicas, internal-only ingress shell-api.gosec.internal,
  EJBCA SERVER cert.
  ServiceEntry for auth.gosec.cloud (vestigial — discovery now uses
  in-cluster path; keeping for ad-hoc curl from inside pods).
  Added to keycloak/allow-keycloak-clients AuthorizationPolicy out of band.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

go.mod

@@ -0,0 +1,31 @@
+module github.com/gosec/gsc-shell-api
+
+go 1.23
+
+require (
+	github.com/coreos/go-oidc/v3 v3.11.0
+	github.com/gofiber/fiber/v2 v2.52.5
+	github.com/jackc/pgx/v5 v5.7.1
+)
+
+require (
+	github.com/andybalholm/brotli v1.0.5 // indirect
+	github.com/go-jose/go-jose/v4 v4.0.2 // indirect
+	github.com/google/uuid v1.5.0 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
+	github.com/jackc/puddle/v2 v2.2.2 // indirect
+	github.com/klauspost/compress v1.17.0 // indirect
+	github.com/mattn/go-colorable v0.1.13 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/mattn/go-runewidth v0.0.15 // indirect
+	github.com/rivo/uniseg v0.2.0 // indirect
+	github.com/valyala/bytebufferpool v1.0.0 // indirect
+	github.com/valyala/fasthttp v1.51.0 // indirect
+	github.com/valyala/tcplisten v1.0.0 // indirect
+	golang.org/x/crypto v0.27.0 // indirect
+	golang.org/x/oauth2 v0.21.0 // indirect
+	golang.org/x/sync v0.8.0 // indirect
+	golang.org/x/sys v0.25.0 // indirect
+	golang.org/x/text v0.18.0 // indirect
+)