feat: Python SDK real implementation + API ingestion routes

- SDK: client with BatchTransport, trace decorator/context manager,
  log_decision, thread-local context stack, nested trace→span support
- API: POST /api/traces (batch ingest), GET /api/traces (paginated list),
  GET /api/traces/[id] (full trace with relations), GET /api/health
- Tests: 8 unit tests for SDK (all passing)
- Transport: thread-safe buffer with background flush thread

apps/web/src/lib/prisma.ts

@@ -0,0 +1,9 @@
+import { PrismaClient } from "@agentlens/database";
+
+const globalForPrisma = globalThis as unknown as {
+  prisma: PrismaClient | undefined;
+};
+
+export const prisma = globalForPrisma.prisma ?? new PrismaClient();
+
+if (process.env.NODE_ENV !== "production") globalForPrisma.prisma = prisma;