docs: Document deployment and dependency management policies

[herokwon]

🔍 Description

Document the implemented deployment and dependency management policies and add them to the project's documentation index.

🗝️ Key Changes

Document Deployment Policies

• Add deployment and release policies covering Preview, Production, and Hotfix deployments.
• Document release version handling, deployment observability, and automation boundaries.

Document Dependency Management Policies

• Add dependency update and auto-merge policies for production and development dependencies.
• Document the Wrangler Worker type synchronization invariant for dependency updates.

Update Documentation Index

• Add the new Deployment and Dependency Management documents to docs/README.md.

🔗 Reference

• fix(github/deployment): Improve Production Worker deployment handling #17
• chore(github): Automate Dependabot Wrangler type synchronization #21
• fix(github/deployment): Support validated hotfix deployments #28

➕ Additional Information

• Documentation focuses on policies, invariants, boundaries, and operationally significant behavior rather than workflow implementation details.
• Existing configuration files remain the source of truth for GitHub Actions, Dependabot, and other implementation-specific settings.
• No application or deployment behavior is changed by this PR.

✅ Checklist

• My code follows the Commit Message Convention of this project.
• I have performed a self-review of my own code.
• For 🧪 Test changes, all tests passed successfully.
• For 🧩 Style changes, code formatting is consistent.
• I have removed unnecessary logs, comments, or debug code.

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Status	✅ Success!
Environment	preview
Pull Request	docs: Document deployment and dependency management policies
Commit	27c945e
URL	https://3cfa73bf-blog.wooyng825.workers.dev
Author	herokwon
Details	➡️ GitHub Actions ➡️ Cloudflare Dashboard