Clean up obsolete CalDAV environment variables

## Removed Obsolete Environment Variables:
- `CALDAV_SERVER_URL` - provided by user login
- `CALDAV_USERNAME` - provided by user login
- `CALDAV_PASSWORD` - provided by user login
- `CALDAV_TASKS_PATH` - not used in any features

## Kept with Intelligent Discovery:
- `CALDAV_CALENDAR_PATH` - optional override, defaults to smart discovery

## Changes:
### Backend
- Remove `CalDAVConfig::from_env()` method (not used in main app)
- Add `CalDAVConfig::new()` constructor with credentials
- Remove `tasks_path` field from CalDAVConfig
- Update auth service to use new constructor
- Update tests to use hardcoded test values instead of env vars
- Update debug tools to use test credentials

### Frontend
- Remove unused `config.rs` file entirely (frontend uses backend API)

## Current Authentication Flow:
1. User provides CalDAV credentials via login API
2. Backend creates CalDAVConfig dynamically from login request
3. Backend tests authentication via calendar discovery
4. Optional `CALDAV_CALENDAR_PATH` env var can override discovery
5. No environment variables required for normal operation

This simplifies deployment - users only need to provide CalDAV
credentials through the web interface, no server-side configuration required.

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

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

backend/src/config.rs

@@ -17,14 +17,16 @@ use base64::prelude::*;
 /// 
 /// ```rust
 /// # use calendar_backend::config::CalDAVConfig;
-/// # fn example() -> Result<(), Box<dyn std::error::Error>> {
-/// // Load configuration from environment variables
-/// let config = CalDAVConfig::from_env()?;
+/// let config = CalDAVConfig {
+///     server_url: "https://caldav.example.com".to_string(),
+///     username: "user@example.com".to_string(), 
+///     password: "password".to_string(),
+///     calendar_path: None,
+///     tasks_path: None,
+/// };
 /// 
 /// // Use the configuration for HTTP requests
 /// let auth_header = format!("Basic {}", config.get_basic_auth());
-/// # Ok(())
-/// # }
 /// ```
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct CalDAVConfig {
@@ -41,74 +43,37 @@ pub struct CalDAVConfig {
     
     /// Optional path to the calendar collection on the server
     /// 
-    /// If not provided, the client will need to discover available calendars
+    /// If not provided, the client will discover available calendars
     /// through CalDAV PROPFIND requests
     pub calendar_path: Option<String>,
-    
-    /// Optional path to the tasks/todo collection on the server
-    /// 
-    /// Some CalDAV servers store tasks separately from calendar events
-    pub tasks_path: Option<String>,
 }
 
 impl CalDAVConfig {
-    /// Creates a new CalDAVConfig by loading values from environment variables.
+    /// Creates a new CalDAVConfig with the given credentials.
     /// 
-    /// This method will attempt to load a `.env` file from the current directory
-    /// and then read the following required environment variables:
+    /// # Arguments
     /// 
-    /// - `CALDAV_SERVER_URL`: The CalDAV server base URL
-    /// - `CALDAV_USERNAME`: Username for authentication
-    /// - `CALDAV_PASSWORD`: Password for authentication
-    /// 
-    /// Optional environment variables:
-    /// 
-    /// - `CALDAV_CALENDAR_PATH`: Path to calendar collection
-    /// - `CALDAV_TASKS_PATH`: Path to tasks collection
-    /// 
-    /// # Errors
-    /// 
-    /// Returns `ConfigError::MissingVar` if any required environment variable
-    /// is not set or cannot be read.
+    /// * `server_url` - The base URL of the CalDAV server
+    /// * `username` - Username for authentication
+    /// * `password` - Password for authentication
     /// 
     /// # Example
     /// 
     /// ```rust
     /// # use calendar_backend::config::CalDAVConfig;
-    /// 
-    /// match CalDAVConfig::from_env() {
-    ///     Ok(config) => {
-    ///         println!("Loaded config for server: {}", config.server_url);
-    ///     }
-    ///     Err(e) => {
-    ///         eprintln!("Failed to load config: {}", e);
-    ///     }
-    /// }
+    /// let config = CalDAVConfig::new(
+    ///     "https://caldav.example.com".to_string(),
+    ///     "user@example.com".to_string(), 
+    ///     "password".to_string()
+    /// );
     /// ```
-    pub fn from_env() -> Result<Self, ConfigError> {
-        // Attempt to load .env file, but don't fail if it doesn't exist
-        dotenvy::dotenv().ok();
-
-        let server_url = env::var("CALDAV_SERVER_URL")
-            .map_err(|_| ConfigError::MissingVar("CALDAV_SERVER_URL".to_string()))?;
-
-        let username = env::var("CALDAV_USERNAME")
-            .map_err(|_| ConfigError::MissingVar("CALDAV_USERNAME".to_string()))?;
-
-        let password = env::var("CALDAV_PASSWORD")
-            .map_err(|_| ConfigError::MissingVar("CALDAV_PASSWORD".to_string()))?;
-
-        // Optional paths - it's fine if these are not set
-        let calendar_path = env::var("CALDAV_CALENDAR_PATH").ok();
-        let tasks_path = env::var("CALDAV_TASKS_PATH").ok();
-
-        Ok(CalDAVConfig {
+    pub fn new(server_url: String, username: String, password: String) -> Self {
+        Self {
             server_url,
             username,
             password,
-            calendar_path,
-            tasks_path,
-        })
+            calendar_path: env::var("CALDAV_CALENDAR_PATH").ok(), // Optional override from env
+        }
     }
 
     /// Generates a Base64-encoded string for HTTP Basic Authentication.
@@ -192,9 +157,12 @@ mod tests {
     /// Run with: `cargo test test_baikal_auth`
     #[tokio::test]
     async fn test_baikal_auth() {
-        // Load config from .env
-        let config = CalDAVConfig::from_env()
-            .expect("Failed to load CalDAV config from environment");
+        // Use test config - update these values to test with real server
+        let config = CalDAVConfig::new(
+            "https://example.com".to_string(),
+            "test_user".to_string(),
+            "test_password".to_string()
+        );
 
         println!("Testing authentication to: {}", config.server_url);
 
@@ -238,8 +206,12 @@ mod tests {
     /// Run with: `cargo test test_propfind_calendars`
     #[tokio::test]
     async fn test_propfind_calendars() {
-        let config = CalDAVConfig::from_env()
-            .expect("Failed to load CalDAV config from environment");
+        // Use test config - update these values to test with real server  
+        let config = CalDAVConfig::new(
+            "https://example.com".to_string(),
+            "test_user".to_string(),
+            "test_password".to_string()
+        );
 
         let client = reqwest::Client::new();