feat(mcpd): McpToken schema + CRUD routes + introspection

Adds a new McpToken Prisma model (project-scoped, SHA-256 hashed at rest,
optional expiry, revocable) plus backing repository, service, and REST
routes. Tokens are a first-class RBAC subject: new 'McpToken' kind is
added to the subject enum and the service auto-creates an RbacDefinition
with subject McpToken:<sha> when bindings are provided.

Creator-permission ceiling: the service rejects any requested binding
the creator cannot already satisfy themselves (re-uses
rbacService.canAccess / canRunOperation). rbacMode=clone snapshots the
creator's full permissions into the token.

Routes:
  POST   /api/v1/mcptokens              create (returns raw token once)
  GET    /api/v1/mcptokens              list (filter by project)
  GET    /api/v1/mcptokens/:id          describe (no secret in response)
  POST   /api/v1/mcptokens/:id/revoke   soft-delete + remove RbacDef
  DELETE /api/v1/mcptokens/:id          hard-delete
  GET    /api/v1/mcptokens/introspect   validate raw bearer (used by mcplocal)

Extends AuditEvent with optional tokenName/tokenSha fields (indexed) so
token-driven activity can be filtered later. Adds token helpers in
@mcpctl/shared: TOKEN_PREFIX='mcpctl_pat_', generateToken, hashToken,
isMcpToken, timingSafeEqualHex.

Follow-up PRs add the auth-hook dispatch on the prefix, the CLI verbs,
and the HTTP-mode mcplocal that calls /introspect.

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

src/shared/src/index.ts

@@ -3,3 +3,4 @@ export * from './validation/index.js';
 export * from './constants/index.js';
 export * from './utils/index.js';
 export * from './secrets/index.js';
+export * from './tokens/index.js';

src/shared/src/tokens/index.ts

@@ -0,0 +1,41 @@
+import { createHash, randomBytes, timingSafeEqual } from 'node:crypto';
+
+export const TOKEN_PREFIX = 'mcpctl_pat_';
+
+// base62 alphabet (URL/header safe, no ambiguous chars across all positions)
+const BASE62 = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+
+export interface GeneratedToken {
+  /** The raw token — `mcpctl_pat_<32 base62 chars>`. Shown once at create time; never stored. */
+  raw: string;
+  /** SHA-256 hex digest of the raw value. Persist this, not the raw value. */
+  hash: string;
+  /** First 16 chars of the raw token, safe to display (e.g. in `mcpctl get mcptoken`). */
+  prefix: string;
+}
+
+export function generateToken(): GeneratedToken {
+  const bytes = randomBytes(24);
+  let body = '';
+  for (const b of bytes) body += BASE62[b % 62];
+  const raw = TOKEN_PREFIX + body;
+  return { raw, hash: hashToken(raw), prefix: raw.slice(0, 16) };
+}
+
+export function hashToken(raw: string): string {
+  return createHash('sha256').update(raw).digest('hex');
+}
+
+export function isMcpToken(bearer: string): boolean {
+  return bearer.startsWith(TOKEN_PREFIX);
+}
+
+/** Constant-time compare two equal-length hex strings. Returns false on length mismatch. */
+export function timingSafeEqualHex(a: string, b: string): boolean {
+  if (a.length !== b.length) return false;
+  try {
+    return timingSafeEqual(Buffer.from(a, 'hex'), Buffer.from(b, 'hex'));
+  } catch {
+    return false;
+  }
+}