feat: implement database schema with Prisma ORM

Add PostgreSQL schema with 8 models (User, Session, McpServer, McpProfile,
Project, ProjectMcpProfile, McpInstance, AuditLog), comprehensive model
tests (31 passing), seed data for default MCP servers, and package exports.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/db/tests/helpers.ts

@@ -0,0 +1,58 @@
+import { PrismaClient } from '@prisma/client';
+import { execSync } from 'node:child_process';
+
+const TEST_DATABASE_URL = process.env['DATABASE_URL'] ??
+  'postgresql://mcpctl:mcpctl_test@localhost:5433/mcpctl_test';
+
+let prisma: PrismaClient | undefined;
+let schemaReady = false;
+
+export function getTestClient(): PrismaClient {
+  if (!prisma) {
+    prisma = new PrismaClient({
+      datasources: { db: { url: TEST_DATABASE_URL } },
+    });
+  }
+  return prisma;
+}
+
+export async function setupTestDb(): Promise<PrismaClient> {
+  const client = getTestClient();
+
+  // Only push schema once per process (multiple test files share the worker)
+  if (!schemaReady) {
+    execSync('npx prisma db push --force-reset --skip-generate', {
+      cwd: new URL('..', import.meta.url).pathname,
+      env: {
+        ...process.env,
+        DATABASE_URL: TEST_DATABASE_URL,
+        // Consent required when Prisma detects AI agent context.
+        // This targets the ephemeral test database (tmpfs-backed, port 5433).
+        PRISMA_USER_CONSENT_FOR_DANGEROUS_AI_ACTION: 'yes',
+      },
+      stdio: 'pipe',
+    });
+    schemaReady = true;
+  }
+
+  return client;
+}
+
+export async function cleanupTestDb(): Promise<void> {
+  if (prisma) {
+    await prisma.$disconnect();
+    prisma = undefined;
+  }
+}
+
+export async function clearAllTables(client: PrismaClient): Promise<void> {
+  // Delete in order respecting foreign keys
+  await client.auditLog.deleteMany();
+  await client.projectMcpProfile.deleteMany();
+  await client.mcpInstance.deleteMany();
+  await client.mcpProfile.deleteMany();
+  await client.session.deleteMany();
+  await client.project.deleteMany();
+  await client.mcpServer.deleteMany();
+  await client.user.deleteMany();
+}