Add copy to clipboard button in editor

Claude-Session: https://claude.ai/code/session_01PoLmSR1pFVyHf8i5b1rNWk

src-tauri/capabilities/default.json

@@ -17,6 +17,8 @@
     "opener:allow-reveal-item-in-dir",
     "dialog:default",
     "dialog:allow-open",
-    "dialog:allow-save"
+    "dialog:allow-save",
+    "clipboard-manager:allow-write-text",
+    "clipboard-manager:allow-write-image"
   ]
 }