Add Tauri ACL capabilities for event listener

Tauri v2 requires explicit permission grants. The SidecarSetup
component uses listen() from @tauri-apps/api/event to receive
download progress, which requires core:event:allow-listen.

Added default capability with core, event, shell, dialog, and
process permissions.

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

src-tauri/capabilities/default.json

@@ -0,0 +1,14 @@
+{
+  "identifier": "default",
+  "description": "Default permissions for the main window",
+  "windows": ["main"],
+  "permissions": [
+    "core:default",
+    "core:event:default",
+    "core:event:allow-listen",
+    "core:event:allow-emit",
+    "shell:default",
+    "dialog:default",
+    "process:default"
+  ]
+}