feat: add prisma skills to claude plugin

[AmanVarshney01]

Summary

• Add the curated Prisma skills package to the Claude plugin, including ORM, Client, Postgres, Compute, database setup, and v7 upgrade guidance.
• Update Claude plugin metadata, local marketplace metadata, README, icon asset, and MCP server config.
• Align the Claude package with the richer Prisma plugin content while keeping this repo Claude-focused.

Validation

• claude plugin validate /Users/aman/dev/work/claude-plugin
• claude plugin validate /Users/aman/dev/work/claude-plugin/.claude-plugin/plugin.json
• npx skills add . --list
• PRISMA_COMPUTE_RUNNER=bunx node skills/prisma-compute/scripts/verify-compute-surface.mjs
• jq empty .claude-plugin/plugin.json .claude-plugin/marketplace.json .mcp.json
• git diff --check