feat: revamp to dynamic database-first architecture and cleanup phase docs

- Migrate document fetching and CRUD to be PostgreSQL-authoritative
- Remove static section enums and add dynamic listSections query
- Support custom sections and metadata across API, MCP, and Web UI
- Add /api/sections endpoint and update Header, Sidebar, and Forms
- Remove obsolete phase planning docs and modernize README/AGENTS

apps/mcp/src/auth.test.ts

@@ -36,6 +36,7 @@ mock.module("@mcpedia/core", () => ({
   keywordSearch: () => Promise.resolve([]),
   getDocument: () => Promise.resolve(null),
   listDocuments: () => Promise.resolve([]),
+  listSections: () => Promise.resolve([]),
   getRelated: () => Promise.resolve([]),
   semanticSearch: () => Promise.resolve([]),
   hybridSearch: () => Promise.resolve([]),
@@ -209,6 +210,7 @@ test("tool discovery works without auth (read tools present)", async () => {
   expect(names).toContain("search_documents");
   expect(names).toContain("get_document");
   expect(names).toContain("list_documents");
+  expect(names).toContain("list_sections");
   expect(names).toContain("semantic_search");
   expect(names).toContain("hybrid_search");
   expect(names).toContain("get_related_documents");