improve url validation

pages/api/sources/check.ts

@@ -12,8 +12,21 @@ type CheckResponse = {
 
 function extractDomain(url: string): string {
   try {
-    const urlObj = new URL(url)
-    return urlObj.hostname.replace('www.', '')
+    // Clean up the URL first
+    let cleanUrl = url.trim()
+    if (!cleanUrl.startsWith('http://') && !cleanUrl.startsWith('https://')) {
+      cleanUrl = 'https://' + cleanUrl
+    }
+    
+    const urlObj = new URL(cleanUrl)
+    let domain = urlObj.hostname.toLowerCase()
+    
+    // Remove common prefixes
+    domain = domain.replace(/^www\./, '')
+    domain = domain.replace(/^m\./, '')
+    domain = domain.replace(/^mobile\./, '')
+    
+    return domain
   } catch {
     return ''
   }