[create-cloudflare] Upgrade OpenAPI template to chanfana 3 and Zod v4

[G4brym]

Upgrade the OpenAPI worker template from chanfana v2 (Zod v3) to chanfana v3.3 (Zod v4).

Changes:

• Bump chanfana from ^2.6.3 to ^3.3.0 and zod from ^3.24.1 to ^4.0.0
• Replace all removed chanfana parameter helpers (Str, Bool, Num, DateTime) with native Zod v4 equivalents (z.string(), z.boolean(), z.number(), z.iso.date())
• Use chanfana's NotFoundException in taskFetch.ts instead of manual Response.json() for 404 responses
• Fix due_date field to use z.iso.date() (matching the actual date-only example data) instead of DateTime() which mapped to datetime format

Migration reference: https://chanfana.pages.dev/migration-to-chanfana-3

---

• Tests
  • Tests included/updated
  • Automated tests not possible - manual testing has been completed as follows:
  • Additional testing not necessary because: This is a template-only change — template type-checks cleanly with the updated dependencies. No runtime tests exist for templates.
• Public documentation
  • Cloudflare docs PR(s):
  • Documentation not necessary because: No user-facing doc changes needed; chanfana's own migration guide covers the API changes.

[changeset-bot]

🦋 Changeset detected

Latest commit: ef45eb7

The changes in this PR will be included in the next version bump.

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[pkg-pr-new]

create-cloudflare

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@cloudflare/kv-asset-handler

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miniflare

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@cloudflare/vitest-pool-workers

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@cloudflare/workers-editor-shared

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wrangler

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commit: ef45eb7

[G4brym]

This solves #13441

[workers-devprod]

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