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/prisma/migrations/20260104203746_add_labels_table/migration.sql

@@ -0,0 +1,16 @@
+-- CreateTable
+CREATE TABLE "Label" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "name" TEXT NOT NULL,
+    "color" TEXT NOT NULL DEFAULT 'gray',
+    "userId" TEXT,
+    "createdAt" DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" DATETIME NOT NULL,
+    CONSTRAINT "Label_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User" ("id") ON DELETE CASCADE ON UPDATE CASCADE
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "Label_name_key" ON "Label"("name");
+
+-- CreateIndex
+CREATE INDEX "Label_userId_idx" ON "Label"("userId");