Polish tool font and border consistency

[vuon9]

Summary

• standardize visible tool micro-labels from 10px to 11px across tool pages and shared tool input/copy controls
• normalize the standout barcode empty-state border from a thick primary-tinted border to the standard border token
• reduce color swatch borders to the standard 1px token
• add a Playwright visual-style consistency guard for all tool pages in light and dark themes

Verification

• RED check: new style audit failed before changes on barcode/color-converter/cron
• bun run test: 35 passed
• bun run build: passed
• bunx playwright test e2e/tool-style-consistency.spec.js --project=chromium: 32 passed
• bunx playwright test e2e/every-page.spec.js --project=chromium: 32 passed
• bunx prettier --check changed files: passed
• git diff --check: passed

[github-actions]

Package	Line Rate	Health
devtoolbox/internal/barcode	93%	✔
devtoolbox/internal/codeformatter	80%	➖
devtoolbox/internal/converter	65%	➖
devtoolbox/internal/datagenerator	81%	✔
devtoolbox/internal/datetimeconverter	75%	➖
devtoolbox/internal/jwt	47%	❌
devtoolbox/internal/numberconverter	98%	✔
devtoolbox/internal/settings	0%	❌
devtoolbox/internal/themes	0%	❌
Summary	70% (3726 / 5294)	➖

Minimum allowed line rate is 60%