v0.5.2 — Add ESLint + typescript-eslint, fix lint errors

Add flat-config ESLint with typescript-eslint recommended rules,
fix all lint errors (unused imports/vars, empty catches, Function types,
prefer-const, useless assignments), and rename stale kpc- CSS class to kcc-.

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

src/main/logger.ts

@@ -67,7 +67,7 @@ function makeLogger(getStream: () => WriteStream) {
 
 export const electronLog = makeLogger(() => electronStream);
 
-export function getLogPath(type: 'electron'): string {
+export function getLogPath(_type: 'electron'): string {
   init();
   return electronPath;
 }