fix: enable createUpdaterArtifacts for Tauri 2 updater signing

Tauri 2 requires 'createUpdaterArtifacts' in the bundle config to
generate .sig signature files alongside installers. Without this,
the TAURI_SIGNING_PRIVATE_KEY env var is ignored and tauri-action
logs 'Signature not found for the updater JSON. Skipping upload...'
on every platform.

Set to 'v1Compatible' which produces the signature format expected
by tauri-plugin-updater and the latest.json manifest.

Author: proofofprints

src-tauri/tauri.conf.json

@@ -33,6 +33,7 @@
     "active": true,
     "targets": "all",
     "publisher": "Proof of Prints",
+    "createUpdaterArtifacts": "v1Compatible",
     "icon": [
       "icons/32x32.png",
       "icons/128x128.png",