Add user information and calendar list to sidebar

Backend changes:
- Add /api/user/info endpoint to fetch user details and calendar list
- Create UserInfo and CalendarInfo models for API responses
- Filter out generic calendar collections from sidebar display
- Extract readable calendar names with proper title case formatting

Frontend changes:
- Fetch and display user info (username, server URL) in sidebar header
- Show list of user's calendars with hover effects and styling
- Add loading states and error handling for user info
- Reorganize sidebar layout: header, navigation, calendar list, logout

Styling:
- Enhanced sidebar with user info section and calendar list
- Responsive design hides user info and calendar list on mobile
- Improved logout button positioning in sidebar footer
- Professional styling with proper spacing and visual hierarchy

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

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

styles.css

@@ -45,15 +45,39 @@ body {
 }
 
 .sidebar-header h1 {
-    margin: 0;
+    margin: 0 0 1rem 0;
     font-size: 1.8rem;
     font-weight: 600;
     text-align: center;
 }
 
+.user-info {
+    text-align: center;
+    margin-bottom: 0.5rem;
+}
+
+.user-info .username {
+    font-size: 1.1rem;
+    font-weight: 600;
+    color: white;
+    margin-bottom: 0.25rem;
+}
+
+.user-info .server-url {
+    font-size: 0.8rem;
+    color: rgba(255,255,255,0.7);
+    word-break: break-all;
+    line-height: 1.2;
+}
+
+.user-info.loading {
+    font-size: 0.9rem;
+    color: rgba(255,255,255,0.6);
+    font-style: italic;
+}
+
 .sidebar-nav {
-    flex: 1;
-    padding: 1.5rem 1rem;
+    padding: 1rem;
     display: flex;
     flex-direction: column;
     gap: 0.5rem;
@@ -80,6 +104,65 @@ body {
     box-shadow: 0 2px 4px rgba(0,0,0,0.1);
 }
 
+.calendar-list {
+    flex: 1;
+    padding: 1rem;
+    border-top: 1px solid rgba(255,255,255,0.1);
+}
+
+.calendar-list h3 {
+    color: white;
+    font-size: 1rem;
+    font-weight: 600;
+    margin: 0 0 1rem 0;
+    text-transform: uppercase;
+    letter-spacing: 0.5px;
+}
+
+.calendar-list ul {
+    list-style: none;
+    margin: 0;
+    padding: 0;
+    display: flex;
+    flex-direction: column;
+    gap: 0.5rem;
+}
+
+.calendar-list li {
+    display: flex;
+    align-items: center;
+    padding: 0.5rem 0.75rem;
+    background: rgba(255,255,255,0.1);
+    border-radius: 6px;
+    transition: all 0.2s;
+    cursor: pointer;
+}
+
+.calendar-list li:hover {
+    background: rgba(255,255,255,0.15);
+    transform: translateX(2px);
+}
+
+.calendar-name {
+    color: white;
+    font-size: 0.9rem;
+    font-weight: 500;
+}
+
+.no-calendars {
+    padding: 1rem;
+    text-align: center;
+    color: rgba(255,255,255,0.6);
+    font-size: 0.9rem;
+    font-style: italic;
+    border-top: 1px solid rgba(255,255,255,0.1);
+}
+
+.sidebar-footer {
+    padding: 1rem;
+    border-top: 1px solid rgba(255,255,255,0.1);
+}
+
 .app-main {
     flex: 1;
     margin-left: 280px;
@@ -200,13 +283,12 @@ body {
     cursor: pointer;
     transition: all 0.2s;
     font-weight: 500;
-    margin-top: auto;
-    margin-bottom: 1rem;
+    width: 100%;
 }
 
 .logout-button:hover {
     background: rgba(255,255,255,0.2);
-    transform: translateX(4px);
+    transform: translateY(-1px);
 }
 
 /* Calendar View */
@@ -549,6 +631,10 @@ body {
         margin: 0;
     }
 
+    .user-info {
+        display: none; /* Hide user info on mobile to save space */
+    }
+
     .sidebar-nav {
         flex-direction: row;
         padding: 0;
@@ -566,6 +652,16 @@ body {
         margin: 0;
         padding: 0.5rem 0.75rem;
         font-size: 0.9rem;
+        width: auto;
+    }
+
+    .calendar-list {
+        display: none; /* Hide calendar list on mobile */
+    }
+
+    .sidebar-footer {
+        padding: 0;
+        border-top: none;
     }
 
     .app-main {