feat: Add empty StatusBar component

- Create StatusBar component with 30px fixed height
- Position at bottom of app layout with proper flex column structure
- Add placeholders for vim mode (left) and sync status (right)
- Reorganize App layout to accommodate status bar below main content

src/view/status_bar.rs

@@ -0,0 +1,31 @@
+use gpui::{Context, IntoElement, Render, Window, div, prelude::*, px};
+
+use crate::theme::ActiveTheme;
+
+pub struct StatusBar {
+    // TODO: Add vim_mode, sync_state, last_sync, etc.
+}
+
+impl StatusBar {
+    pub fn new(_cx: &mut Context<Self>) -> Self {
+        Self {}
+    }
+}
+
+impl Render for StatusBar {
+    fn render(&mut self, _window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        let theme = cx.theme().clone();
+
+        div()
+            .flex()
+            .items_center()
+            .justify_between()
+            .w_full()
+            .h(px(30.0))
+            .px_4()
+            .py_1()
+            .bg(theme.panel)
+            .border_b_1()
+            .border_color(theme.border)
+    }
+}