build: migrate eslint to v10 flat config and upgrade typescript

Replace .eslintrc.json with eslint.config.js using the new flat config
format required by ESLint 10. Swap @typescript-eslint/eslint-plugin and
@typescript-eslint/parser for the unified typescript-eslint package.
Upgrade TypeScript to 5.9 and @types/node to 25. Apply automatic code
fixes: remove unused catch bindings and preserve error cause in auth
header parsing.

lib/ui/db.ts

@@ -260,7 +260,7 @@ function flattenPreset(
     try {
       // Try parse to check expression validity
       parse(p.precondition as string);
-    } catch (error) {
+    } catch {
       p.precondition = convertOldPrecondition(
         JSON.parse(p.precondition as string),
       );