feat: rename keep-notes to memento-note, migrate to PostgreSQL, fix MCP bugs

- Rename directory keep-notes -> memento-note with all code references
- Prisma: SQLite -> PostgreSQL (both app and MCP server schemas)
- Sync MCP schema with main app (add missing fields, relations, indexes)
- Delete 17 SQLite migrations (clean slate for PostgreSQL)
- Remove SQLite dependencies (@libsql/client, better-sqlite3, etc.)
- Fix MCP server: hardcoded Windows DB paths -> DATABASE_URL env var
- Fix MCP server: .dockerignore excluded index-sse.js (SSE mode broken)
- MCP Dockerfile: node:20 -> node:22
- Docker Compose: add postgres service, remove SQLite volume
- Generate favicon.ico, icon-192.png, icon-512.png, apple-icon.png
- Update layout.tsx icons and manifest.json for PNG icons
- Update all .env files for PostgreSQL
- Rewrite README.md with updated sections
- Remove mcp-server/node_modules and prisma/client-generated from git tracking

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

memento-note/lib/prisma.ts

@@ -0,0 +1,23 @@
+// @ts-ignore - Generated client
+import { PrismaClient } from '../prisma/client-generated'
+
+const prismaClientSingleton = () => {
+  return new PrismaClient({
+    datasources: {
+      db: {
+        url: process.env.DATABASE_URL,
+      },
+    },
+  })
+}
+
+declare const globalThis: {
+  prismaGlobal: ReturnType<typeof prismaClientSingleton>;
+} & typeof global;
+
+const prisma = globalThis.prismaGlobal ?? prismaClientSingleton()
+
+export { prisma }
+export default prisma
+
+if (process.env.NODE_ENV !== 'production') globalThis.prismaGlobal = prisma