feat(ui): optimize responsive dashboard workflows

[mikewong23571]

Summary

This PR turns CPA Usage Keeper into a more focused operational console for spotting request-health, cost, quota, and credential issues across desktop and mobile.

• rebuilds the shared application shell and page structure on the existing Ant Design stack
• establishes Request Health and Total Cost as the primary Overview metrics
• keeps Request Health Timeline as the product-specific reliability signature
• improves Analysis chart hierarchy, sizing, resize behavior, and screen-reader data alternatives
• makes Request Events usable as a 7-to-21-column table through internal scrolling, stable widths, ellipsis, accessible tooltips, and a frozen timestamp column
• aligns Auth File and AI Provider credential surfaces while keeping secondary expiry metadata inside expanded details
• preserves Login, API Key Viewer, CPAMC Embed, light/dark themes, and Chinese/English layouts
• adds executable responsive, accessibility, and style-governance coverage
• reports incomplete pricing coverage instead of presenting an unverified zero cost

The implementation and acceptance criteria are documented in:

• docs/UI_OPTIMIZATION_PLAN_AND_ACCEPTANCE.md
• docs/UI_OPTIMIZATION_ACCEPTANCE_REPORT.md

Why

The previous UI gave many metrics equal visual weight, allowed wide data surfaces to compete with page scrolling, and accumulated page-local layout rules. That made reliability and cost anomalies slower to scan and made responsive behavior harder to predict.

This change consolidates those rules into shared shell, semantic theme, section, and component boundaries. Decorative accents that duplicated icon meaning were removed, while secondary credential metadata is available on demand rather than occupying the default table.

Screenshots

Overview — desktop

Overview — mobile

Analysis

Request Events — wide table

Validation

• make verify
  • Go test suite passed
  • 74 frontend test files passed
  • 716 frontend tests passed
  • ESLint passed
  • TypeScript typecheck passed
  • production build passed
• browser acceptance completed in Chrome 150 at 390x844, 768x1024, 1024x768, 1280x720, 1440x900, 1920x1080, and 2560x1440
• required viewports cover English/Chinese and light/dark according to the acceptance contract
• Overview trend rendering adds no API requests or polling
• no new UI runtime dependency was added by the optimization phase

Review notes

The branch is directly based on current upstream main (f4a0755) and is not behind it. The PR is intentionally opened as a draft because it is a broad visual and structural change; the implementation itself has completed the repository verification and documented acceptance matrix.