v0.2.5: feat: URL import UI + adapter routes + docs (M4)

User-facing layer for Upload-from-URL (backend landed in M2):

- Core UI: a gated "Import URL" toolbar button (shown only when the token has
  allow_url_import) + a compact dialog (input → importing → success / error).
  Errors are mapped to human-readable, locale-aware messages (never leak the
  technical code). New import.* + error.* strings across all 16 locales.
- Adapters: Laravel (route + importUrl controller) and WordPress (REST route +
  handleImportUrl) proxy the route; both bump fluxfiles/fluxfiles to ^0.2.15
  (they now reference the new core UrlImporter — the route-parity guard enforces
  the proxy). adapter smokes green.
- Docs: README claims table + import note, CHANGELOG, api-map, CLAUDE.md.

Verified with Playwright: button gating (hidden without the claim), dialog open,
real public URL imports end-to-end into the grid, and an SSRF URL surfaces the
human message. 2 new e2e tests; full browser suite 30/30, PHP 26/26, adapter
smokes 9/9 + 6/6.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>