feat: replace Basic Auth with cookie session auth for admin panel

fix: use server-side logout endpoint to reliably clear Basic Auth credentials

feat: add logout button to admin panel header

chore: ignore reference.md

feat: redesign admin panel with sidebar layout and toast notifications

feat: accept x-api-key as auth token for Anthropic SDK compatibility

fix: strip version prefix from apiPath when baseUrl already contains version

chore: set KV namespace id

chore: add gitignore, design doc, plan, lockfile

fix: empty password guard, json parse error handling, admin error boundary, fetch credentials

feat: worker entry with auth middleware

feat: admin panel and config API

feat: request router and forwarder

feat: KV config helpers

feat: utility functions