Add FastMCP skill to optional-skills/mcp/fastmcp/ with:
- SKILL.md with workflow, design patterns, quality checklist
- Templates: API wrapper, database server, file processor
- Scaffold CLI script for template instantiation
- FastMCP CLI reference documentation
Moved to optional-skills (requires pip install fastmcp).
Based on work by kshitijk4poor in PR #2096.
Closes#343
