chore: migrate the toolchain to TypeScript 7

[ydj515]

Summary

Migrate the project from TypeScript 6.0.3 to TypeScript 7 after the lint and build toolchain supports it, while preserving path aliases, generated routes, tests, Storybook, and E2E behavior.

Background

Dependabot PR #42 attempted to upgrade TypeScript to 7.0.2. The update was excluded from #43 because the current toolchain is not yet compatible.

Observed blockers:

• typescript-eslint@8.67.0 declares a TypeScript peer range of >=4.8.4 <6.1.0.
• TypeScript 7 validation fails with TS5102 because baseUrl has been removed.
• TypeScript 7 validation fails with TS5090 because the existing path targets are not explicitly relative.
• The errors occur in both tsconfig.app.json and tsconfig.vitest.json.

Node 24.19.0 and pnpm 11.22.0 are already pinned. jsdom 30 is already supported and is not part of this migration blocker.

Scope

• Select a typescript-eslint release that explicitly supports TypeScript 7, or document and approve another compatible lint strategy without suppressing peer checks.
• Remove baseUrl from tsconfig.app.json and tsconfig.vitest.json.
• Update the @/* path target to an explicitly relative TypeScript 7-compatible value.
• Upgrade TypeScript and regenerate pnpm-lock.yaml with pnpm 11.22.0.
• Verify TanStack Router route generation, Vite builds, Vitest coverage, Storybook, and Playwright.
• Do not manually edit src/routeTree.gen.ts; regenerate it with pnpm generate-routes.

Acceptance Criteria

• pnpm peers check reports no peer dependency issues.
• pnpm typecheck passes without TS5102 or TS5090.
• pnpm verify passes.
• pnpm audit --audit-level high passes.
• GitHub CI succeeds for Validate, Storybook, Playwright E2E, and Security audit.
• Documentation reflects the supported TypeScript version if it is version-specific.

References

• Dependabot attempt: chore(deps-dev): bump the dev-dependencies group across 1 directory with 24 updates #42
• Compatible dependency consolidation: chore: update Node, pnpm, and compatible dependencies #43