feat(routing): routing_rules schema + types — M4-001/002/003 (#315)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/gateway/src/agent/provider-credentials.dto.ts

@@ -0,0 +1,23 @@
+/** DTO for storing a provider credential. */
+export interface StoreCredentialDto {
+  /** Provider identifier (e.g., 'anthropic', 'openai', 'openrouter', 'zai') */
+  provider: string;
+  /** Credential type */
+  type: 'api_key' | 'oauth_token';
+  /** Plain-text credential value — will be encrypted before storage */
+  value: string;
+  /** Optional extra config (e.g., base URL overrides) */
+  metadata?: Record<string, unknown>;
+}
+
+/** DTO returned in list/existence responses — never contains decrypted values. */
+export interface ProviderCredentialSummaryDto {
+  provider: string;
+  credentialType: 'api_key' | 'oauth_token';
+  /** Whether a credential is stored for this provider */
+  exists: boolean;
+  expiresAt?: string | null;
+  metadata?: Record<string, unknown> | null;
+  createdAt: string;
+  updatedAt: string;
+}