Fix timezone display: client uses server timezone from settings, revert SQL offset

server/index.js

@@ -230,9 +230,8 @@ app.get('/api/dashboard', (req, res) => {
       WHERE resource_id = ? AND resolved_at IS NULL
     `).get(resource.id);
 
-    const tzOffset = getTimezoneOffset();
     const recentChecks = db.prepare(`
-      SELECT response_time, status, datetime(checked_at, '${tzOffset}') as checked_at
+      SELECT response_time, status, checked_at
       FROM checks
       WHERE resource_id = ?
       ORDER BY checked_at DESC
@@ -455,7 +454,6 @@ app.get('/api/resources/:id/history', (req, res) => {
     WHERE resource_id = ? AND checked_at > datetime('now', ?)
   `).get(id, `-${days} days`);
 
-  const tzOffset = getTimezoneOffset();
   const checks = db.prepare(`
     SELECT 
       id,
@@ -464,7 +462,7 @@ app.get('/api/resources/:id/history', (req, res) => {
       status_code,
       error_message,
       details,
-      datetime(checked_at, '${tzOffset}') as checked_at
+      checked_at
     FROM checks
     WHERE resource_id = ? AND checked_at > datetime('now', ?)
     ORDER BY checked_at DESC
@@ -541,11 +539,10 @@ app.get('/api/history/overview', (req, res) => {
       // Use a reliable bucketing approach with Julian Day Numbers
       // Convert to julian day, multiply by 24 for hours, divide by intervalHours and round
       const bucketExpr = `ROUND((julianday(checked_at) * 24) / ${intervalHours}) * ${intervalHours} / 24`;
-      const tzOffset = getTimezoneOffset();
       
       recentChecks = db.prepare(`
         SELECT 
-          datetime(${bucketExpr}, '${tzOffset}') AS checked_at,
+          datetime(${bucketExpr}) AS checked_at,
           AVG(CASE WHEN status='up' THEN response_time ELSE NULL END) AS avg_up_response,
           SUM(CASE WHEN status='up' THEN 1 ELSE 0 END) AS up_count,
           COUNT(*) AS total_count
@@ -562,9 +559,8 @@ app.get('/api/history/overview', (req, res) => {
     } else {
       console.log(`Using non-averaged mode for ${resource.name}`);
       // Non-averaged: filter to window but cap to last 600 checks
-      const tzOffset = getTimezoneOffset();
       recentChecks = db.prepare(`
-        SELECT status, response_time, datetime(checked_at, '${tzOffset}') as checked_at
+        SELECT status, response_time, checked_at
         FROM checks
         WHERE resource_id = ? AND checked_at > datetime('now', ?)
         ORDER BY checked_at DESC