Fix desktop app not being able to load pdfium (#6575)

# Description of Changes
The changes in
[#6279](https://github.com/Stirling-Tools/Stirling-PDF/pull/6279) broke
the desktop app because the wasm URL handling didn't deal with
`tauri://` paths. Also I noticed that `task desktop:build:dev:mac`
failed locally because it was attempting to sign the app with
credentials that developers won't have (and shouldn't need), so I fixed
that too.

.taskfiles/desktop.yml

@@ -62,21 +62,21 @@ tasks:
     deps: [prepare]
     dir: editor
     cmds:
-      - npx tauri build --bundles app
+      - npx tauri build --bundles app --config '{"bundle":{"createUpdaterArtifacts":false}}'
 
   build:dev:windows:
     desc: "Build Tauri desktop NSIS installer (Windows)"
     deps: [prepare]
     dir: editor
     cmds:
-      - npx tauri build --bundles nsis
+      - npx tauri build --bundles nsis --config '{"bundle":{"createUpdaterArtifacts":false}}'
 
   build:dev:linux:
     desc: "Build Tauri desktop AppImage (Linux)"
     deps: [prepare]
     dir: editor
     cmds:
-      - npx tauri build --bundles appimage
+      - npx tauri build --bundles appimage --config '{"bundle":{"createUpdaterArtifacts":false}}'
 
   test:
     desc: "Run Tauri/Cargo tests"