chore(lint): enable strict ESLint rules and fix unused-vars violations (F4.1)

Enable no-console (warn, allow error), @typescript-eslint/no-unused-vars
(warn, ignore _ prefix), and @typescript-eslint/no-explicit-any (warn).
Fix all 26 no-unused-vars violations across 9 files.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/components/CustomFieldsDisplay.vue

@@ -81,7 +81,7 @@
 </template>
 
 <script setup>
-import { ref, reactive, onMounted, watch, computed } from 'vue'
+import { reactive, onMounted, watch, computed } from 'vue'
 
 const props = defineProps({
   customFields: {