feat(web): add data table example with sorting, filtering, and pagination

[GRACENOBLE]

Problem

There is no data table pattern in the web layer. Every feature that lists data will need to independently solve sorting, filtering, and pagination.

Acceptance criteria

• Add a components/data-table/ using TanStack Table v8 + shadcn/ui table primitives
• Support: column sorting, text filter input, and page-based pagination
• Include a working example using mock/static data (no real API required)
• Add a Vitest component test for the table
• Document usage in web/docs/components.md (or create it)

[GRACENOBLE]

Implemented and merged via PR #66.