Add tests to all packages, remove passWithNoTests

Every package now has tests — no more empty test suites:

- map-core: 33 tests — maxspeedColor, routeGradeColor, elevationColor,
  POI categories, getCategoriesForProfile, tile layer configs
- db: 5 tests — withDb error handling (503 on DB error, re-throws
  Response/DataWithResponseInit, logs errors)
- ui: 14 tests — Button variants/sizes/disabled, Input label/id/error,
  Card className forwarding
- map: 2 tests — baseLayers/overlayLayers re-export verification

Remove passWithNoTests from vitest.shared.ts so missing tests are
caught immediately when adding new packages.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vitest.shared.ts

@@ -2,7 +2,6 @@ import { defineConfig } from "vitest/config";
 
 export default defineConfig({
   test: {
-    passWithNoTests: true,
     include: ["src/**/*.test.{ts,tsx}", "app/**/*.test.{ts,tsx}"],
   },
 });