Add CalDAV integration tests with Baikal server

- Updated base64 usage to new API (BASE64_STANDARD.encode)
- Added tokio dev dependency for async testing
- Created comprehensive integration tests:
  - test_baikal_auth: Tests authentication with OPTIONS request
  - test_propfind_calendars: Tests calendar discovery with PROPFIND
- Tests validate:
  - HTTP Basic Auth with .env credentials
  - DAV server capabilities detection
  - CalDAV PROPFIND XML responses
  - 207 Multi-Status handling
- Both tests pass successfully against Baikal server
- Tests marked as #[ignore] for CI/network isolation

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

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

src/config.rs

@@ -1,5 +1,6 @@
 use serde::{Deserialize, Serialize};
 use std::env;
+use base64::prelude::*;
 
 /// Configuration for CalDAV server connection and authentication.
 /// 
@@ -137,7 +138,7 @@ impl CalDAVConfig {
     /// ```
     pub fn get_basic_auth(&self) -> String {
         let credentials = format!("{}:{}", self.username, self.password);
-        base64::encode(&credentials)
+        BASE64_STANDARD.encode(&credentials)
     }
 }
 
@@ -163,7 +164,6 @@ pub enum ConfigError {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use std::env;
 
     #[test]
     fn test_basic_auth_encoding() {
@@ -176,7 +176,111 @@ mod tests {
         };
 
         let auth = config.get_basic_auth();
-        let expected = base64::encode("testuser:testpass");
+        let expected = BASE64_STANDARD.encode("testuser:testpass");
         assert_eq!(auth, expected);
     }
+
+    /// Integration test that authenticates with the actual Baikal CalDAV server
+    /// 
+    /// This test requires a valid .env file with:
+    /// - CALDAV_SERVER_URL
+    /// - CALDAV_USERNAME  
+    /// - CALDAV_PASSWORD
+    /// 
+    /// Run with: `cargo test test_baikal_auth -- --ignored`
+    #[tokio::test]
+    #[ignore] // Ignored by default since it requires network access and valid credentials
+    async fn test_baikal_auth() {
+        // Load config from .env
+        let config = CalDAVConfig::from_env()
+            .expect("Failed to load CalDAV config from environment");
+
+        println!("Testing authentication to: {}", config.server_url);
+
+        // Create HTTP client
+        let client = reqwest::Client::new();
+
+        // Make a simple OPTIONS request to test authentication
+        let response = client
+            .request(reqwest::Method::OPTIONS, &config.server_url)
+            .header("Authorization", format!("Basic {}", config.get_basic_auth()))
+            .header("User-Agent", "calendar-app/0.1.0")
+            .send()
+            .await
+            .expect("Failed to send request to CalDAV server");
+
+        println!("Response status: {}", response.status());
+        println!("Response headers: {:#?}", response.headers());
+
+        // Check if we got a successful response or at least not a 401 Unauthorized
+        assert!(
+            response.status().is_success() || response.status() != 401,
+            "Authentication failed with status: {}. Check your credentials in .env",
+            response.status()
+        );
+
+        // For Baikal/CalDAV servers, we should see DAV headers
+        assert!(
+            response.headers().contains_key("dav") || 
+            response.headers().contains_key("DAV") ||
+            response.status().is_success(),
+            "Server doesn't appear to be a CalDAV server - missing DAV headers"
+        );
+
+        println!("✓ Authentication test passed!");
+    }
+
+    /// Test making a PROPFIND request to discover calendars
+    /// 
+    /// This test requires a valid .env file and makes an actual CalDAV PROPFIND request
+    /// 
+    /// Run with: `cargo test test_propfind_calendars -- --ignored`
+    #[tokio::test]
+    #[ignore]
+    async fn test_propfind_calendars() {
+        let config = CalDAVConfig::from_env()
+            .expect("Failed to load CalDAV config from environment");
+
+        let client = reqwest::Client::new();
+
+        // CalDAV PROPFIND request to discover calendars
+        let propfind_body = r#"<?xml version="1.0" encoding="utf-8" ?>
+<d:propfind xmlns:d="DAV:" xmlns:c="urn:ietf:params:xml:ns:caldav">
+    <d:prop>
+        <d:resourcetype />
+        <d:displayname />
+        <c:calendar-description />
+        <c:supported-calendar-component-set />
+    </d:prop>
+</d:propfind>"#;
+
+        let response = client
+            .request(reqwest::Method::from_bytes(b"PROPFIND").unwrap(), &config.server_url)
+            .header("Authorization", format!("Basic {}", config.get_basic_auth()))
+            .header("Content-Type", "application/xml")
+            .header("Depth", "1")
+            .header("User-Agent", "calendar-app/0.1.0")
+            .body(propfind_body)
+            .send()
+            .await
+            .expect("Failed to send PROPFIND request");
+
+        let status = response.status();
+        println!("PROPFIND Response status: {}", status);
+        
+        let body = response.text().await.expect("Failed to read response body");
+        println!("PROPFIND Response body: {}", body);
+
+        // We should get a 207 Multi-Status for PROPFIND
+        assert_eq!(
+            status,
+            reqwest::StatusCode::from_u16(207).unwrap(),
+            "PROPFIND should return 207 Multi-Status"
+        );
+
+        // The response should contain XML with calendar information
+        assert!(body.contains("calendar"), "Response should contain calendar information");
+
+        println!("✓ PROPFIND calendars test passed!");
+    }
 }