feat(m7.3): cross-tenant admin HTTP endpoints

Adds two cross-tenant operator endpoints on top of the M7.2-D
DatabasePool primitives:
- GET    /api/v1/admin/tenants              → list tenant DBs
- DELETE /api/v1/admin/tenants/{tenant_id}  → drop (GDPR delete)

Auth is a static bearer (ADMIN_API_TOKEN env), explicitly NOT a
Keycloak JWT — the whole point is to operate across tenants and a
customer JWT always carries a single tenant_id, which would be a
semantic conflict. Comparison is constant-time to avoid byte-level
timing probes.

Design
- ADMIN_API_TOKEN env on the agent. When unset, the admin routes
  aren't mounted at all (404 rather than 401). An operator who
  hasn't opted in can't fingerprint the surface.
- Admin sub-router is built in start_api_server when the token is
  configured, then merged into the main router with its own
  require_admin_token middleware.
- compliance-core::auth gains a PUBLIC_PREFIXES list. Paths under
  /api/v1/admin/ bypass require_jwt_auth so the customer JWT path
  and the admin token path never collide.
- require_tenant_status passes through naturally — admin requests
  carry no TenantContext.

Files
- compliance-core/src/auth.rs — PUBLIC_PREFIXES + prefix-aware skip.
- compliance-core/src/config.rs — admin_api_token + tenant_registry_url
  fields on AgentConfig. tenant_registry_url is added now so the
  scheduler→registry PR doesn't have to bump the config shape again.
- compliance-agent/src/config.rs — env wiring for both.
- compliance-agent/src/api/handlers/admin.rs (new) — list_tenant_dbs,
  drop_tenant_db, require_admin_token middleware, tokens_eq helper
  with a small test.
- compliance-agent/src/api/server.rs — conditional admin sub-router
  + merge.
- Test harness fixtures updated for the two new config fields.

Test plan
- cargo fmt --all clean
- cargo clippy --workspace --exclude compliance-dashboard
  -- -D warnings clean
- cargo test -p compliance-core --lib — 7 pass
- cargo test -p compliance-agent --lib — 229 pass (+1 new for
  tokens_eq)

Production
- Set ADMIN_API_TOKEN in orca-infra (per-secret, NOT committed) when
  ready to expose these endpoints. Without the env, the routes
  literally don't exist on the binary.
- Long-term: replace the static bearer with a dedicated admin realm
  in Keycloak. Token rotation is just an env change + restart for
  now; revocation responsiveness is zero.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

compliance-core/src/auth.rs

@@ -63,16 +63,24 @@ struct Claims {
 
 const PUBLIC_ENDPOINTS: &[&str] = &["/api/v1/health"];
 
+/// Path prefixes that bypass JWT validation. The admin sub-router
+/// (`/api/v1/admin/*`) has its own static-bearer middleware and must
+/// not be routed through the customer-JWT path — a Keycloak token
+/// always carries a single tenant_id and would semantically conflict
+/// with cross-tenant admin operations.
+const PUBLIC_PREFIXES: &[&str] = &["/api/v1/admin/"];
+
 /// Middleware that validates Bearer JWT tokens against Keycloak's JWKS
 /// and attaches a `TenantContext` extension on success.
 ///
-/// Skips validation for the health endpoint.
-/// If `JwksState` is not present (Keycloak not configured), requests
-/// pass through and downstream code must handle the missing context.
+/// Skips validation for the health endpoint and any path under one of
+/// the [`PUBLIC_PREFIXES`]. If `JwksState` is not present (Keycloak
+/// not configured), requests pass through and downstream code must
+/// handle the missing context.
 pub async fn require_jwt_auth(mut request: Request, next: Next) -> Response {
     let path = request.uri().path();
 
-    if PUBLIC_ENDPOINTS.contains(&path) {
+    if PUBLIC_ENDPOINTS.contains(&path) || PUBLIC_PREFIXES.iter().any(|p| path.starts_with(p)) {
         return next.run(request).await;
     }
 

compliance-core/src/config.rs

@@ -37,6 +37,15 @@ pub struct AgentConfig {
     pub pentest_imap_tls: bool,
     pub pentest_imap_username: Option<String>,
     pub pentest_imap_password: Option<SecretString>,
+    /// Static bearer for the cross-tenant admin endpoints under
+    /// `/api/v1/admin/*`. When `None`, those endpoints are not
+    /// mounted at all (defense-in-depth: ops endpoints never reach
+    /// any auth path if no operator has explicitly opted in).
+    pub admin_api_token: Option<SecretString>,
+    /// Live tenant-registry URL the scheduler consults for the list
+    /// of tenants to iterate. When `None` or unreachable, scheduler
+    /// falls back to `SCHEDULER_TENANT_IDS` env (M7.2-C).
+    pub tenant_registry_url: Option<String>,
 }
 
 #[derive(Clone, Debug, Serialize, Deserialize)]