Bookmark Manager REST API

Problem/Feature Description

A developer is building a personal bookmark manager as a Go HTTP service with SQLite as the storage backend. The service exposes a REST API using the standard net/http package (no frameworks).

The service needs to support:

• Adding a bookmark with a URL, title, optional description, and one or more folder names
• Listing all bookmarks, with optional filtering by folder
• Getting a single bookmark by ID
• Updating a bookmark's title and description
• Deleting a bookmark (should also remove its folder associations)
• Creating and listing folders

Each bookmark has: id (integer primary key), url (unique), title, description, created_at. Each folder has: id (integer primary key), name (unique). A join table bookmark_folders links bookmarks to folders.

Output Specification

Produce:

• main.go -- HTTP server setup and routing
• db.go -- Database connection and migrations
• handlers.go -- HTTP handler functions
• store.go -- Database query functions (data access layer)
• go.mod -- Module file with dependencies

The code should be complete Go with no placeholders or TODO comments.