Log raw response when Garmin returns non-JSON

Garmin is returning HTML error pages instead of JSON data. This
change reads the response as text first, checks if it starts with
{ or [, and logs the first 1000 chars of the response body if not.

This will help diagnose what page Garmin is returning (login, captcha,
rate limit, etc).

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

src/lib/garmin.ts

@@ -72,7 +72,15 @@ export async function fetchHrvStatus(
       return "Unknown";
     }
 
-    const data = await response.json();
+    const text = await response.text();
+    if (!text.startsWith("{") && !text.startsWith("[")) {
+      logger.error(
+        { endpoint: "hrv-service", responseBody: text.slice(0, 1000) },
+        "Garmin returned non-JSON response",
+      );
+      return "Unknown";
+    }
+    const data = JSON.parse(text);
     const status = data?.hrvSummary?.status;
 
     if (status === "BALANCED") {
@@ -120,7 +128,15 @@ export async function fetchBodyBattery(
       return { current: null, yesterdayLow: null };
     }
 
-    const data = await response.json();
+    const text = await response.text();
+    if (!text.startsWith("{") && !text.startsWith("[")) {
+      logger.error(
+        { endpoint: "bodyBattery", responseBody: text.slice(0, 1000) },
+        "Garmin returned non-JSON response",
+      );
+      return { current: null, yesterdayLow: null };
+    }
+    const data = JSON.parse(text);
 
     const currentData = data?.bodyBatteryValuesArray?.[0];
     const current = currentData?.charged ?? null;
@@ -170,7 +186,15 @@ export async function fetchIntensityMinutes(
       return 0;
     }
 
-    const data = await response.json();
+    const text = await response.text();
+    if (!text.startsWith("{") && !text.startsWith("[")) {
+      logger.error(
+        { endpoint: "fitnessstats", responseBody: text.slice(0, 1000) },
+        "Garmin returned non-JSON response",
+      );
+      return 0;
+    }
+    const data = JSON.parse(text);
     const weeklyTotal = data?.weeklyTotal;
 
     if (!weeklyTotal) {