Adds GET /admin index redirect, createdAt date-range filtering on the
transactions list with a stat strip (total/success/pending/revenue) and
client-side search, plus inline validation and quick amount chips on the
new-transaction form.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017KPzWwuTEeX2vXGXvyGn4q