feat(kon): replace browser clipboard with arboard

- New copy_to_clipboard Tauri command using arboard 3.6
- Replaced all 5 navigator.clipboard.writeText() calls across
  DictationPage, HistoryPage, FilesPage, and viewer with invoke()
- Native clipboard access independent of WebView permissions

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/lib/pages/DictationPage.svelte

@@ -332,7 +332,7 @@
   async function finaliseTranscription() {
     if (transcript.trim()) {
       if (settings.autoCopy) {
-        navigator.clipboard.writeText(transcript).catch(() => {});
+        invoke("copy_to_clipboard", { text: transcript }).catch(() => {});
       }
 
       // Save audio if enabled — capture path for history replay
@@ -395,7 +395,7 @@
   }
 
   function copyAll() {
-    if (transcript) navigator.clipboard.writeText(transcript).catch(() => {});
+    if (transcript) invoke("copy_to_clipboard", { text: transcript }).catch(() => {});
   }
 
   function clearTranscript() {

src/lib/pages/FilesPage.svelte

@@ -117,7 +117,7 @@
   }
 
   function copyAll() {
-    if (fileTranscript) navigator.clipboard.writeText(fileTranscript);
+    if (fileTranscript) invoke("copy_to_clipboard", { text: fileTranscript }).catch(() => {});
   }
 
   function handleExport(format) {

src/lib/pages/HistoryPage.svelte

@@ -46,7 +46,7 @@
   }
 
   function copyItem(item) {
-    navigator.clipboard.writeText(item.text).catch(() => {});
+    invoke("copy_to_clipboard", { text: item.text }).catch(() => {});
   }
 
   function removeItem(item) {

src/routes/viewer/+page.svelte

@@ -1,7 +1,7 @@
 <script>
   import { onMount, onDestroy } from "svelte";
   import { getCurrentWindow } from "@tauri-apps/api/window";
-  import { convertFileSrc } from "@tauri-apps/api/core";
+  import { convertFileSrc, invoke } from "@tauri-apps/api/core";
   import { formatTime, formatDuration } from "$lib/utils/time.js";
   import { PLAYBACK_SPEEDS } from "$lib/utils/constants.js";
 
@@ -193,7 +193,7 @@
 
   function copySegment(idx) {
     if (item?.segments?.[idx]) {
-      navigator.clipboard.writeText(item.segments[idx].text.trim()).catch(() => {});
+      invoke("copy_to_clipboard", { text: item.segments[idx].text.trim() }).catch(() => {});
     }
   }