Rename Text size to Interface; scale panel header with it

Action buttons, server picker, and its dropdown now follow the size
setting via new --action-h/--action-font/--action-icon variables.
Default tier matches the old fixed sizes; tab bar stays fixed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/shared/types.ts

@@ -69,7 +69,7 @@ export interface AppSettings {
 	/** File-list icons: plain neutral glyphs, or per-category glyphs and colors. */
 	iconColors: "plain" | "multi";
 	speedUnit: "MBps" | "Mbps";
-	/** Font size of the path bar and file list. */
+	/** Size of the panel interface: file list, path bar, header controls. */
 	textSize: "compact" | "default" | "large";
 	/** Run transfer jobs one at a time, or several in parallel. */
 	transferMode: "single" | "multi";