Upgrade eslint tooling to v10 and fix linting bugs (#601)

- Upgrade eslint 9→10, eslint-config-prettier 9→10, eslint-plugin-vue 9→10
- Upgrade @types/node 20→24
- Migrate from legacy .eslintrc.mjs to flat config eslint.config.mjs
- Remove --ext flag from npm test script (dropped in eslint 10)
- Fix vue/no-ref-as-operand: add missing .value to ref assignments (5 files)
- Fix vue/return-in-computed-property: add default returns (2 files)
- Fix vue/no-side-effects-in-computed-properties: move mutation to watcher
- Fix vue/no-dupe-keys: remove ref shadowing prop in DomPDFDriver
- Fix vue/no-deprecated-slot-attribute: migrate to v-slot syntax (3 files)
- Fix vue/require-valid-default-prop: use factory function for array default
- Fix vue/no-unused-vars: remove unused slot destructure
- Disable vue/no-mutating-props (false positive for Pinia store props)

resources/scripts/admin/views/SampleTable.vue

@@ -37,7 +37,7 @@
         </span>
       </template>
 
-      <template #cell-actions="{ row }">
+      <template #cell-actions>
         <base-dropdown width-class="w-48" margin-class="mt-1">
           <template #activator>
             <div class="flex items-center justify-center">