chore: add deploy skill for static site deployment (Claude Code extension)

[rajnavakoti]

Description

Create a reusable `/deploy` Claude Code skill that builds and deploys static sites to Firebase Hosting. Should be generic enough to work across multiple projects.

Acceptance Criteria

• Skill detects build tool (Astro, Vite, Next static) and runs appropriate build command
• Deploys `dist/` (or configured output dir) to Firebase Hosting
• Works as a global skill (usable across projects)
• Includes dry-run option to preview what would be deployed
• Prints the deployed URL on success

Out of Scope

• Cloud Run or server-based deployments
• Multi-cloud support (Firebase only for now)