Remove debug logging from all-day event detection

🤖 Generated with [Claude Code](https://claude.ai/code)

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

backend/src/calendar.rs

@@ -365,8 +365,6 @@ impl CalDAVClient {
         let empty_string = String::new();
         let dtstart_raw = properties.get("DTSTART").unwrap_or(&empty_string);
         let all_day = dtstart_raw.contains("VALUE=DATE") || (!dtstart_raw.contains("T") && dtstart_raw.len() == 8);
-        
-        eprintln!("🔍 DTSTART parsing: '{}' -> all_day: {}", dtstart_raw, all_day);
 
         // Parse status
         let status = properties