feat: align terminal font settings with appearance fonts

- Terminal font dropdown now uses mono fonts from UI font options
- Unified font list between appearance section and terminal settings
- Terminal font persisted to GlobalSettings for import/export support
- Aligned global terminal settings popover with per-terminal popover:
  - Same settings in same order (Font Size, Run on New Terminal, Font Family, Scrollback, Line Height, Screen Reader)
  - Consistent styling (Radix Select instead of native select)
- Added terminal padding (12px vertical, 16px horizontal) for readability

apps/ui/src/styles/global.css

@@ -880,6 +880,11 @@
   background: var(--muted-foreground);
 }
 
+/* Terminal padding for better readability */
+.xterm {
+  padding: 12px 16px;
+}
+
 /* ========================================
    DEPENDENCY GRAPH STYLES
    Theme-aware styling for React Flow graph