Add CalDAV dependencies and secure configuration

- Added comprehensive CalDAV/calendar dependencies:
  - reqwest for HTTP requests
  - ical for calendar parsing
  - chrono for date/time handling
  - serde for serialization
  - anyhow/thiserror for error handling
  - uuid for event generation
- Implemented secure config management:
  - dotenvy for environment variable loading
  - base64 for Basic Auth encoding
  - .env.example template for development
  - .gitignore updated to exclude secret files
- Created config.rs module with extensive documentation:
  - CalDAVConfig struct for server credentials
  - Environment-based configuration loading
  - HTTP Basic Auth helper methods
  - Comprehensive error handling
  - Full rustdoc documentation with examples

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

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

Cargo.toml

@@ -6,4 +6,32 @@ edition = "2021"
 [dependencies]
 yew = { version = "0.21", features = ["csr"] }
 web-sys = "0.3"
-wasm-bindgen = "0.2"
+wasm-bindgen = "0.2"
+
+# HTTP client for CalDAV requests
+reqwest = { version = "0.11", features = ["json"] }
+wasm-bindgen-futures = "0.4"
+
+# Calendar and iCal parsing
+ical = "0.7"
+serde = { version = "1.0", features = ["derive"] }
+serde_json = "1.0"
+
+# Date and time handling
+chrono = { version = "0.4", features = ["serde", "wasm-bindgen"] }
+chrono-tz = "0.8"
+
+# Error handling
+anyhow = "1.0"
+thiserror = "1.0"
+
+# Logging
+log = "0.4"
+console_log = "1.0"
+
+# UUID generation for calendar events
+uuid = { version = "1.0", features = ["v4", "wasm-bindgen"] }
+
+# Environment variable handling
+dotenvy = "0.15"
+base64 = "0.21"