feat: dynamic, scoped API keys (+ restore cmd/server entrypoint)

Validate X-API-Key against a DB-backed, self-managed key store in addition
to the static Infisical keys, so new consumers (e.g. gsc_admin) no longer
require a rebuild. Keys carry scopes (e.g. {ldap:read}); the required scope
is derived per-request from path + method and enforced by ScopeEnforce.
Static Infisical keys keep an implicit wildcard scope (no regression).

- service/apikey.go: DB store (admin.api_keys, SHA-256 hashes only), 30s
  validation cache, generate/list/revoke. EnsureSchema is existence-first
  (to_regclass) so a least-privilege DB role starts cleanly when the table
  is provisioned out-of-band; startup is non-fatal if the store is absent.
- handler/apikeys.go + routes: POST/GET/DELETE /api/v1/admin/api-keys.
- middleware/apikey.go: APIKeyWithValidator + Principal + ScopeEnforce.
- pkg/types/scopes.go: scope vocabulary + matching.
- migrations/002_api_keys.sql.

Also restore cmd/server/main.go, which the `.gitignore` `server` pattern
was silently excluding (it matched cmd/server/); anchored that pattern and
`gsc-ops-api` to the repo root so only the built binaries are ignored.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -1,7 +1,7 @@
 # Build output
 bin/
-gsc-ops-api
-server
+/gsc-ops-api
+/server
 *.bak
 *.bak.*