feat: enhance image import and solvability calculation (v1.13.0)

- Implement non-linear threshold slider (histogram percentile method)
- Add real-time solvability calculation with progress indicator
- Improve solvability logic with generative lookahead (smash)
- Update ImageImportModal UI (alpha preview, grid size 5-80)
- Add missing translations and difficulty labels
- Optimize web worker pool with queue clearing and progress reporting
- Fix mobile camera support and UI layout

package.json

@@ -1,6 +1,6 @@
 {
   "name": "vue-nonograms-solid",
-  "version": "1.12.11",
+  "version": "1.13.0",
   "homepage": "https://nonograms.7u.pl/",
   "type": "module",
   "scripts": {