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/DisplaySettings.vue

@@ -103,7 +103,7 @@
 <script setup>
 import { ref, onMounted } from 'vue'
 
-const props = defineProps({
+defineProps({
   isOpen: {
     type: Boolean,
     default: false