ST-1216: Insights sprint-widget — token KPI-kaartjes & per-job tabel (#114)

* feat(ST-vmc7vpps): lib/insights/token-stats.ts — sprint KPI + per-job query

SQL-queries voor totale tokens/kosten (KPI) en per-job tabel met
ModelPrice JOIN. Guard op lege sprintId. Tests voor empty guard,
KPI-mapping en null token-data.

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

* feat(ST-vmc7vpps): TokenUsageCard — KPI-kaartjes + sorteerbare per-job tabel

Client-component met drie KPI-strips (totaal tokens, kosten USD, gem. per job)
en sorteerbare tabel op kosten of duur. Nulls als '—', MD3-tokens, geen
hardcoded kleuren.

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

* feat(ST-vmc7vpps): insights page — TokenUsageCard integreren

Voeg getTokenStats + TokenUsageCard imports toe aan insights/page.tsx.
tokenStats apart awaiten na activeSprints (kan niet in dezelfde Promise.all).
TokenUsageCard-sectie toegevoegd na AgentThroughputCard.

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

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

__tests__/lib/insights/token-stats.test.ts

@@ -0,0 +1,67 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+
+const { mockQueryRaw } = vi.hoisted(() => ({ mockQueryRaw: vi.fn() }))
+
+vi.mock('@/lib/prisma', () => ({
+  prisma: { $queryRaw: mockQueryRaw },
+}))
+
+import { getTokenStats } from '@/lib/insights/token-stats'
+
+beforeEach(() => {
+  vi.clearAllMocks()
+})
+
+describe('getTokenStats', () => {
+  it('returns empty result for empty sprintId', async () => {
+    const result = await getTokenStats('user-1', '')
+
+    expect(result.kpi.totalTokens).toBe(0)
+    expect(result.kpi.totalCostUsd).toBe(0)
+    expect(result.kpi.avgCostPerJob).toBe(0)
+    expect(result.kpi.jobCount).toBe(0)
+    expect(result.jobs).toHaveLength(0)
+    expect(mockQueryRaw).not.toHaveBeenCalled()
+  })
+
+  it('maps kpi rows correctly', async () => {
+    const kpiRows = [{ total_tokens: BigInt(10000), total_cost: 0.15, avg_cost: 0.05, job_count: BigInt(3) }]
+    const jobRows: unknown[] = []
+    mockQueryRaw.mockResolvedValueOnce(kpiRows).mockResolvedValueOnce(jobRows)
+
+    const result = await getTokenStats('user-1', 'sprint-1')
+
+    expect(result.kpi.totalTokens).toBe(10000)
+    expect(result.kpi.totalCostUsd).toBe(0.15)
+    expect(result.kpi.avgCostPerJob).toBe(0.05)
+    expect(result.kpi.jobCount).toBe(3)
+  })
+
+  it('maps job rows and handles null token data', async () => {
+    const kpiRows = [{ total_tokens: BigInt(0), total_cost: null, avg_cost: null, job_count: BigInt(0) }]
+    const jobRows = [
+      {
+        job_id: 'job-1',
+        task_title: 'My Task',
+        idea_code: null,
+        model_id: 'claude-sonnet-4-6',
+        input_tokens: null,
+        output_tokens: null,
+        cache_read_tokens: null,
+        cache_write_tokens: null,
+        cost_usd: null,
+        duration_seconds: 42,
+      },
+    ]
+    mockQueryRaw.mockResolvedValueOnce(kpiRows).mockResolvedValueOnce(jobRows)
+
+    const result = await getTokenStats('user-1', 'sprint-1')
+
+    expect(result.jobs).toHaveLength(1)
+    const job = result.jobs[0]
+    expect(job.jobId).toBe('job-1')
+    expect(job.taskTitle).toBe('My Task')
+    expect(job.costUsd).toBeNull()
+    expect(job.durationSeconds).toBe(42)
+  })
+})