Implement shared RFC 5545 VEvent library with workspace restructuring

- Created calendar-models/ shared library with RFC 5545-compliant VEvent structures
- Migrated backend to use shared VEvent with proper field mappings (dtstart/dtend, rrule, exdate, etc.)
- Converted CalDAV client to parse into VEvent structures with structured types
- Updated all CRUD handlers to use VEvent with CalendarUser, Attendee, VAlarm types
- Restructured project as Cargo workspace with frontend/, backend/, calendar-models/
- Updated Trunk configuration for new directory structure
- Fixed all compilation errors and field references throughout codebase
- Updated documentation and build instructions for workspace structure

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

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

frontend/src/components/context_menu.rs

@@ -0,0 +1,49 @@
+use yew::prelude::*;
+use web_sys::MouseEvent;
+
+#[derive(Properties, PartialEq)]
+pub struct ContextMenuProps {
+    pub is_open: bool,
+    pub x: i32,
+    pub y: i32,
+    pub on_delete: Callback<MouseEvent>,
+    pub on_close: Callback<()>,
+}
+
+#[function_component(ContextMenu)]
+pub fn context_menu(props: &ContextMenuProps) -> Html {
+    let menu_ref = use_node_ref();
+    
+    // Close menu when clicking outside (handled by parent component)
+
+    if !props.is_open {
+        return html! {};
+    }
+
+    let style = format!(
+        "position: fixed; left: {}px; top: {}px; z-index: 1001;",
+        props.x, props.y
+    );
+
+    let on_delete_click = {
+        let on_delete = props.on_delete.clone();
+        let on_close = props.on_close.clone();
+        Callback::from(move |e: MouseEvent| {
+            on_delete.emit(e);
+            on_close.emit(());
+        })
+    };
+
+    html! {
+        <div 
+            ref={menu_ref}
+            class="context-menu" 
+            style={style}
+        >
+            <div class="context-menu-item context-menu-delete" onclick={on_delete_click}>
+                <span class="context-menu-icon">{"🗑️"}</span>
+                {"Delete Calendar"}
+            </div>
+        </div>
+    }
+}