Fix CSS copying and processing with Trunk

- Use data-trunk directive for CSS processing instead of manual copy
- Enable automatic content hashing and cache busting for styles.css
- Remove unused CalendarInfo import to fix compiler warning
- Simplify Trunk.toml by removing redundant copy configuration

This ensures styles.css is properly copied and processed on every build
with automatic cache invalidation when styles change.

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

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

src/app.rs

@@ -2,7 +2,7 @@ use yew::prelude::*;
 use yew_router::prelude::*;
 use gloo_storage::{LocalStorage, Storage};
 use crate::components::{Login, Calendar};
-use crate::services::{CalendarService, CalendarEvent, UserInfo, CalendarInfo};
+use crate::services::{CalendarService, CalendarEvent, UserInfo};
 use std::collections::HashMap;
 use chrono::{Local, NaiveDate, Datelike};