Fix external calendar creation and Outlook compatibility issues

- Fix external calendar form validation by replacing node refs with controlled state inputs
- Add multiple user-agent fallback approach for better external calendar compatibility
- Enhance HTTP client configuration with proper redirect handling and timeouts
- Add detailed error logging and Outlook-specific error detection
- Improve request headers for better calendar server compatibility

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

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

backend/src/handlers/ics_fetcher.rs

@@ -78,17 +78,75 @@ pub async fn fetch_external_calendar_events(
 
     // If not fetched from cache, get from external URL
     if !fetched_from_cache {
-        let client = Client::new();
-        let response = client
-            .get(&calendar.url)
-            .send()
-            .await
-            .map_err(|e| ApiError::Internal(format!("Failed to fetch calendar: {}", e)))?;
-
-        if !response.status().is_success() {
-            return Err(ApiError::Internal(format!("Calendar server returned: {}", response.status())));
+        // Log the URL being fetched for debugging
+        println!("🌍 Fetching calendar URL: {}", calendar.url);
+        
+        let user_agents = vec![
+            "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36",
+            "Mozilla/5.0 (compatible; Runway Calendar/1.0)",
+            "Outlook-iOS/709.2226530.prod.iphone (3.24.1)"
+        ];
+        
+        let mut response = None;
+        let mut last_error = None;
+        
+        // Try different user agents
+        for (i, ua) in user_agents.iter().enumerate() {
+            println!("🔄 Attempt {} with User-Agent: {}", i + 1, ua);
+            
+            let client = Client::builder()
+                .redirect(reqwest::redirect::Policy::limited(10))
+                .timeout(std::time::Duration::from_secs(30))
+                .user_agent(*ua)
+                .build()
+                .map_err(|e| ApiError::Internal(format!("Failed to create HTTP client: {}", e)))?;
+            
+            let result = client
+                .get(&calendar.url)
+                .header("Accept", "text/calendar,application/calendar+xml,text/plain,*/*")
+                .header("Accept-Charset", "utf-8")
+                .header("Cache-Control", "no-cache")
+                .send()
+                .await;
+                
+            match result {
+                Ok(resp) => {
+                    let status = resp.status();
+                    println!("📡 Response status: {}", status);
+                    if status.is_success() {
+                        response = Some(resp);
+                        break;
+                    } else if status == 400 {
+                        // Check if this is an Outlook auth error
+                        let error_body = resp.text().await.unwrap_or_default();
+                        if error_body.contains("OwaPage") || error_body.contains("Outlook") {
+                            println!("🚫 Outlook authentication error detected, trying next approach...");
+                            last_error = Some(format!("Outlook auth error: {}", error_body.chars().take(100).collect::<String>()));
+                            continue;
+                        }
+                        last_error = Some(format!("Bad Request: {}", error_body.chars().take(100).collect::<String>()));
+                    } else {
+                        last_error = Some(format!("HTTP {}", status));
+                    }
+                }
+                Err(e) => {
+                    println!("❌ Request failed: {}", e);
+                    last_error = Some(format!("Request error: {}", e));
+                }
+            }
         }
+        
+        let response = response.ok_or_else(|| {
+            ApiError::Internal(format!(
+                "Failed to fetch calendar after trying {} different approaches. Last error: {}", 
+                user_agents.len(), 
+                last_error.unwrap_or("Unknown error".to_string())
+            ))
+        })?;
 
+        // Response is guaranteed to be successful here since we checked in the loop
+        println!("✅ Successfully fetched calendar data");
+        
         ics_content = response
             .text()
             .await