Implement full-screen monthly calendar UI

Added a comprehensive monthly calendar component with modern styling:
- Full monthly view with proper date calculations
- Current day highlighting and navigation
- Responsive design for all screen sizes
- Event indicator support for future integration
- Takes up most of screen space as requested

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

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

src/app.rs

@@ -1,7 +1,8 @@
 use yew::prelude::*;
 use yew_router::prelude::*;
 use gloo_storage::{LocalStorage, Storage};
-use crate::components::{Login, Register};
+use crate::components::{Login, Register, Calendar};
+use std::collections::HashMap;
 
 #[derive(Clone, Routable, PartialEq)]
 enum Route {
@@ -104,37 +105,12 @@ pub fn App() -> Html {
 
 #[function_component]
 fn CalendarView() -> Html {
-    let counter = use_state(|| 0);
-    let onclick = {
-        let counter = counter.clone();
-        move |_| {
-            let value = *counter + 1;
-            counter.set(value);
-        }
-    };
-
+    // Sample events for demonstration
+    let events = HashMap::new();
+    
     html! {
         <div class="calendar-view">
-            <h2>{"Welcome to your Calendar!"}</h2>
-            <p>{"You are now authenticated and can access your calendar."}</p>
-            
-            // Temporary counter demo - will be replaced with calendar functionality
-            <div class="demo-section">
-                <h3>{"Demo Counter"}</h3>
-                <button {onclick}>{ "Click me!" }</button>
-                <p>{ format!("Counter: {}", *counter) }</p>
-            </div>
-            
-            <div class="calendar-placeholder">
-                <p>{"Calendar functionality will be implemented here."}</p>
-                <p>{"This will include:"}</p>
-                <ul>
-                    <li>{"Calendar view with events"}</li>
-                    <li>{"Integration with CalDAV server"}</li>
-                    <li>{"Event creation and editing"}</li>
-                    <li>{"Synchronization with Baikal server"}</li>
-                </ul>
-            </div>
+            <Calendar events={events} />
         </div>
     }
 }