Enable ESLint no-unused-vars rule (#4367)

# Description of Changes
Enable ESLint [no-unused-vars
rule](https://typescript-eslint.io/rules/no-unused-vars/)

frontend/scripts/generate-icons.js

@@ -107,7 +107,7 @@ async function main() {
         needsRegeneration = false;
         info(`✅ Icon set already up-to-date (${usedIcons.length} icons, ${Math.round(fs.statSync(outputPath).size / 1024)}KB)`);
       }
-    } catch (error) {
+    } catch {
       // If we can't parse existing file, regenerate
       needsRegeneration = true;
     }

frontend/scripts/generate-licenses.js

@@ -24,7 +24,7 @@ try {
     // Install license-checker if not present
     try {
         require.resolve('license-checker');
-    } catch (e) {
+    } catch {
         console.log('📦 Installing license-checker...');
         execSync('npm install --save-dev license-checker', { stdio: 'inherit' });
     }