URL Shortener Service

Problem/Feature Description

A developer is building a simple URL shortener service in Go with SQLite for persistence. The service should handle moderate traffic (a few hundred requests per minute) and run as a single binary with no external dependencies.

The service needs to support:

• Creating a short URL: accepts a long URL and an optional custom short code. If no custom code is provided, generate a random 7-character alphanumeric code. Return the short code and full short URL.
• Redirecting: given a short code, look up the original URL and redirect (HTTP 301). Increment a click counter on each redirect.
• Getting stats for a short URL: return the original URL, short code, click count, creation date, and last accessed date.
• Listing all URLs with their stats, sorted by creation date
• Deleting a short URL by code

Each URL has: id, short_code (unique), original_url, click_count (default 0), created_at, last_accessed_at.

The click counter update on redirect must be efficient since it happens on every redirect request.

Output Specification

Produce:

• main.go -- HTTP server with routes
• db.go -- Database setup and migrations
• store.go -- URL storage operations
• handlers.go -- HTTP handlers for all endpoints
• go.mod -- Module file

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