feat(paste): auto-insert transcript at cursor via wtype/xdotool/ydotool/osascript/SendKeys

Adds an opt-in "auto-paste into focused window" toggle. When enabled, the
dictation pipeline sets the clipboard and then sends a Ctrl+V / Cmd+V
keystroke to whatever window currently has focus — the common case after a
global-hotkey dictation, since Kon's own window never stole focus.

Backend (src-tauri/src/commands/paste.rs) probes for a platform paste tool
and falls back cleanly:
- Linux Wayland: wtype > ydotool > xdotool
- Linux X11: xdotool > ydotool > wtype
- macOS: osascript System Events keystroke
- Windows: PowerShell WScript.Shell SendKeys

detect_paste_backends is a pure probe used by Settings to describe the
available backend next to the toggle (or nudge the user to install one).
paste_text always copies first, so auto-paste failure degrades to the
existing clipboard-only behaviour and surfaces a warn toast.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/types/app.ts

@@ -36,6 +36,7 @@ export interface SettingsState {
   antiHallucination: boolean;
   britishEnglish: boolean;
   autoCopy: boolean;
+  autoPaste: boolean;
   includeTimestamps: boolean;
   theme: "Dark" | "Light" | "System";
   fontSize: number;