feat: Feature 2.2 — Line Movement + Cascade Detection

Line movement system:
- Baseline capture on first odds fetch of the day
- Movement detection >= 0.5 points with direction (up/down)
- Sharp money heuristic (sharp_action/public_action/unknown)
- GET /api/movements with player, stat_type, min_movement filters
- Movements included in GET /api/odds/nba live responses

Cascade detection system:
- Scratch detection: player props disappear from 2+ books
- Affected user lookup via scan_sessions + picks
- Parlay re-grade without scratched legs
- cascade_alerts created for affected users
- GET /api/alerts (Analyst/Desk only), PATCH /api/alerts/:id/read

Zero extra Odds API credits — all detection piggybacks on existing fetches.
Migration 002: line_baselines, line_movements, cascade_alerts tables.

30 new tests, 188 total (161 Node.js + 27 Python), all passing.
Phase 2 Core Product COMPLETE.

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

tests/unit/alertService.test.js

@@ -0,0 +1,73 @@
+const mockSupabaseFrom = jest.fn();
+jest.mock('../../src/utils/supabase', () => ({
+  getSupabaseServiceClient: () => ({ from: mockSupabaseFrom }),
+}));
+
+const { getAlertsForUser, markAlertRead } = require('../../src/services/alertService');
+
+beforeEach(() => {
+  jest.clearAllMocks();
+});
+
+describe('alertService', () => {
+  test('getAlertsForUser returns unread alerts', async () => {
+    const alerts = [
+      { id: 'a1', alert_type: 'player_scratched', detail: 'Player X scratched', is_read: false },
+    ];
+    mockSupabaseFrom.mockImplementation(() => ({
+      select: (sel, opts) => {
+        if (opts?.head) {
+          return {
+            eq: () => ({ eq: () => Promise.resolve({ count: 1 }) }),
+          };
+        }
+        return {
+          eq: (col, val) => ({
+            eq: () => ({
+              order: () => Promise.resolve({ data: alerts, error: null }),
+            }),
+          }),
+        };
+      },
+    }));
+
+    const result = await getAlertsForUser('user-1');
+    expect(result.alerts).toHaveLength(1);
+    expect(result.unread_count).toBe(1);
+  });
+
+  test('markAlertRead returns updated alert', async () => {
+    mockSupabaseFrom.mockReturnValue({
+      update: () => ({
+        eq: () => ({
+          eq: () => ({
+            select: () => ({
+              single: () => Promise.resolve({ data: { id: 'a1', is_read: true }, error: null }),
+            }),
+          }),
+        }),
+      }),
+    });
+
+    const result = await markAlertRead('a1', 'user-1');
+    expect(result.id).toBe('a1');
+    expect(result.is_read).toBe(true);
+  });
+
+  test('markAlertRead returns null for nonexistent alert', async () => {
+    mockSupabaseFrom.mockReturnValue({
+      update: () => ({
+        eq: () => ({
+          eq: () => ({
+            select: () => ({
+              single: () => Promise.resolve({ data: null, error: { message: 'not found' } }),
+            }),
+          }),
+        }),
+      }),
+    });
+
+    const result = await markAlertRead('nonexistent', 'user-1');
+    expect(result).toBeNull();
+  });
+});