feat(cloudflare/zone): add Zone resource

[agcty]

Adds a first-class Cloudflare Zone resource for zone-scoped infrastructure.

• supports creating or adopting zones by name
• exposes zone attributes needed by follow-on resources
• supports mutable type, paused, and vanityNameServers patching
• supports delete: false for retained production zones
• registers Zone in the Cloudflare provider collection

Verification run:

• bun vitest run packages/alchemy/test/Cloudflare/Zone/Zone.test.ts
• bun tsc -b --pretty false
• git diff --check

[agcty]

Verification update:

• Focused test passed without live env: bun vitest run packages/alchemy/test/Cloudflare/Zone/Zone.test.ts (skipped as expected).
• Typecheck passed: bun tsc -b --pretty false.
• Live test passed against the real Cloudflare zone sneef.xyz using env credentials and an isolated temporary Alchemy profile. The test adopted the existing zone with delete: false, preserved current mutable zone settings, destroyed local state, and verified the zone was retained.