fix MCP read tools: add storyboard + search endpoints, remove dead hub tool

[esot321c]

Summary

• Add storyboard overview endpoint (GET /storyboard) returning all plotlines and works with chapter/scene counts
• Add search endpoint stub (GET /projects/:slug/search) — returns empty results pending Prisma contains implementation
• Remove dead get_entity_hub MCP tool (entity detail endpoint already serves full hub data)
• Simplify get_storyboard MCP tool to use the new overview endpoint
• Update TODO.md and MCP_IMPLEMENTATION_PLAN.md: mark Phases 1–2 complete, expand Phase 3 read tool coverage from 7 to 12 tools, reorder phases to prioritize reads + search before review queue

Test

• Setup an API key from the UX
• Added the MCP server to Claude Code
• Claude Code was able to use the tools and get information about a project.