Fix body battery showing zeros on dashboard after Garmin sync

PocketBase coerces null number fields to 0 when reading. When Garmin
API returned no data (null), we stored null, which became 0 on
retrieval. The nullish coalescing (?? 100) in the API route didn't
catch this because 0 is not nullish.

Now store default value 100 when Garmin returns null, matching the
existing pattern used for decision engine calculations.

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

src/app/api/cron/garmin-sync/route.test.ts

@@ -457,7 +457,11 @@ describe("POST /api/cron/garmin-sync", () => {
       expect(body.errors).toBe(1);
     });
 
-    it("handles body battery null values", async () => {
+    it("stores default value 100 when body battery is null from Garmin", async () => {
+      // When Garmin API returns null for body battery values (no data available),
+      // we store the default value 100 instead of null.
+      // This prevents PocketBase's number field null-to-0 coercion from causing
+      // the dashboard to display 0 instead of a meaningful value.
       mockUsers = [createMockUser()];
       mockFetchBodyBattery.mockResolvedValue({
         current: null,
@@ -468,8 +472,8 @@ describe("POST /api/cron/garmin-sync", () => {
 
       expect(mockPbCreate).toHaveBeenCalledWith(
         expect.objectContaining({
-          bodyBatteryCurrent: null,
-          bodyBatteryYesterdayLow: null,
+          bodyBatteryCurrent: 100,
+          bodyBatteryYesterdayLow: 100,
         }),
       );
     });

src/app/api/cron/garmin-sync/route.ts

@@ -205,13 +205,16 @@ export async function POST(request: Request) {
       );
 
       // Create DailyLog entry
+      // Store default value 100 for body battery when Garmin returns null.
+      // This prevents PocketBase's number field null-to-0 coercion from
+      // causing the dashboard to display 0 instead of a meaningful value.
       await pb.collection("dailyLogs").create({
         user: user.id,
         date: today,
         cycleDay,
         phase,
-        bodyBatteryCurrent: bodyBattery.current,
-        bodyBatteryYesterdayLow: bodyBattery.yesterdayLow,
+        bodyBatteryCurrent: bodyBattery.current ?? 100,
+        bodyBatteryYesterdayLow: bodyBattery.yesterdayLow ?? 100,
         hrvStatus,
         weekIntensityMinutes,
         phaseLimit,