Add reusable UI components: ConfirmDialog, EditableSlider, Vite type declarations

- ConfirmDialog: modal confirm with Escape/backdrop dismiss, danger styling, i18n labels
- EditableSlider: click-to-edit numeric slider with clamping and keyboard support
- vite-env.d.ts: type declarations for .txt raw imports
- Fixed missing title prop in EditableSlider interface from PR

vite-env.d.ts

@@ -0,0 +1,12 @@
+/// <reference types="vite/client" />
+
+// Declare .txt file imports as raw text
+declare module '*.txt' {
+  const content: string;
+  export default content;
+}
+
+declare module '*.txt?raw' {
+  const content: string;
+  export default content;
+}