Rework 0.5.0: harden runtime and contracts

[Endogen]

Summary

Web2API 0.5.0 hardening rework (originally codex/rework-0.5.0), plus a CI fix.

Runtime hardening

• Centralized outbound-network SSRF guard (network_security.py) for both browser (Playwright route interception) and httpx requests, with WEB2API_ALLOW_PRIVATE_NETWORK escape hatch.
• BaseScraper.requires_browser so pure-HTTP/CLI scrapers skip the browser pool.
• Typed endpoint parameters (type/enum/minimum/maximum/pattern/min_length/max_length) with validation + coercion.
• Separate admin token (WEB2API_ADMIN_TOKEN) and 403 gate for recipe-management endpoints.
• MCP server DNS-rebinding protection (configurable hosts/origins).

Reliability & ops

• Atomic, 0600-permissioned manifest writes and atomic recipe install with rollback.
• Upload limits (WEB2API_MAX_UPLOAD_FILES/WEB2API_MAX_UPLOAD_BYTES, streamed), accepts_files gating, q max length.
• Trust now fails closed (entry_is_trusted).
• Docker image de-bloated (drop nodejs/npm/bird, migrate to uv), added .dockerignore.
• Version bump to 0.5.0.

CI

• Fix uv sync to install the dev extra (--extra dev), so ruff/pytest are available.

Depends on companion recipes PR for the 0.5.0 recipe contracts.