test(pitch-deck): vitest setup + tests for auth + admin-auth + rate-limit

Adds vitest with 36 tests covering the security primitives:

- lib/auth: token gen uniqueness, hashToken determinism, JWT roundtrip,
  validateAdminSecret bearer flow, getClientIp x-forwarded-for parsing
- lib/admin-auth: bcrypt hash uniqueness/verify, JWT roundtrip,
  audience claim isolation (admin JWT does not validate as investor JWT)
- lib/rate-limit: limit enforcement, key isolation, window reset via
  fake timers, preset config sanity

Pure-function coverage only — route handler integration tests would
need a test DB and are deferred.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pitch-deck/vitest.config.ts

@@ -0,0 +1,16 @@
+import { defineConfig } from 'vitest/config'
+import path from 'path'
+
+export default defineConfig({
+  test: {
+    environment: 'node',
+    include: ['__tests__/**/*.test.ts'],
+    setupFiles: ['./__tests__/setup.ts'],
+    globals: false,
+  },
+  resolve: {
+    alias: {
+      '@': path.resolve(__dirname, '.'),
+    },
+  },
+})