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/composables/useCategoryEditGuard.ts

@@ -57,7 +57,7 @@ export function useCategoryEditGuard (config: GuardConfig) {
           : 0
 
       linkedCount.value = extractTotal(result.data, fallbackLength)
-    } catch (error) {
+    } catch (_error) {
       linkedCount.value = 0
     } finally {
       linkedLoading.value = false