Fix Garmin intensity minutes and add user-configurable phase goals

- Apply 2x multiplier for vigorous intensity minutes (matches Garmin)
- Use calendar week (Mon-Sun) instead of trailing 7 days for intensity
- Add HRV yesterday fallback when today's data returns empty
- Add user-configurable phase intensity goals with new defaults:
  - Menstrual: 75, Follicular: 150, Ovulation: 100
  - Early Luteal: 120, Late Luteal: 50
- Update garmin-sync and today routes to use user-specific phase limits

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/api/today/route.test.ts

@@ -77,6 +77,11 @@ describe("GET /api/today", () => {
     notificationTime: "07:00",
     timezone: "America/New_York",
     activeOverrides: [],
+    intensityGoalMenstrual: 75,
+    intensityGoalFollicular: 150,
+    intensityGoalOvulation: 100,
+    intensityGoalEarlyLuteal: 120,
+    intensityGoalLateLuteal: 50,
     created: new Date("2024-01-01"),
     updated: new Date("2025-01-10"),
     ...overrides,
@@ -369,7 +374,7 @@ describe("GET /api/today", () => {
       const body = await response.json();
 
       expect(body.phaseConfig.name).toBe("FOLLICULAR");
-      expect(body.phaseConfig.weeklyLimit).toBe(120);
+      expect(body.phaseConfig.weeklyLimit).toBe(150);
     });
 
     it("returns days until next phase", async () => {