feat(shell): add Ctrl+/- zoom and display all shortcuts in footer

- Ctrl+/Ctrl-/Ctrl+0 to zoom in/out/reset terminal font size
- Zoom badge indicator in tab bar
- All shell shortcuts now shown in statusbar footer
- Added i18n labels for search, zoom, switch tab, next tab

💘 Generated with Crush

Assisted-by: GLM-5.1 via Crush <crush@charm.land>

web/src/components/App.jsx

@@ -94,6 +94,10 @@ export default function App() {
     shell: [
       { keys: `${layout.keys.ctrl}+${layout.keys.shift}+C`, desc: t('statusbar.copy') },
       { keys: `${layout.keys.ctrl}+${layout.keys.shift}+V`, desc: t('statusbar.paste') },
+      { keys: `${layout.keys.ctrl}+F`, desc: t('statusbar.search') },
+      { keys: `${layout.keys.ctrl}+/Ctrl−`, desc: t('statusbar.zoom') },
+      { keys: `Alt+1-7`, desc: t('statusbar.switchTab') },
+      { keys: `${layout.keys.shift}+Tab`, desc: t('statusbar.nextTab') },
       { keys: layout.keys.enter, desc: t('statusbar.runCommand') },
       { keys: `${layout.keys.up}/${layout.keys.down}`, desc: t('statusbar.commandHistory') },
     ],