Replace in-memory database with SQLite

[art049]

Summary

This PR replaces the in-memory slice-based album storage with a persistent SQLite database implementation.

Changes

Database Setup

• Added SQLite driver dependency (github.com/mattn/go-sqlite3)
• Created initDB() function to initialize SQLite database with schema
• Database file albums.db stores persistent album data
• Automatic seeding with initial album data on first run

Data Model

• Changed album ID from string to int64 to support auto-increment primary keys
• Added proper database schema with NOT NULL constraints

API Handlers

• GET /albums: Updated to query all albums from database with proper error handling
• POST /albums: Now inserts albums into database and returns generated ID
• GET /albums/:id: Replaced slice iteration with SQL query by ID

Testing

• Updated benchmark tests to work with database-generated IDs
• Removed hard-coded ID from POST benchmark test
• Fixed invalid JSON test case

Error Handling

• Added proper error responses for database operations
• Distinguish between "not found" (404) and internal errors (500)

Test Plan

• All API endpoints work with SQLite backend
• Database is created and seeded on first run
• Benchmark tests pass with new implementation

🤖 Generated with Claude Code

Co-Authored-By: Claude noreply@anthropic.com

[codspeed-hq]

CodSpeed Performance Report

Merging #1 will degrade performances by 85.89%

_{Comparing feature/sqlite-database (3c7d0e9) with main (769218c)}

Summary

❌ 3 regressions
✅ 3 untouched

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	BenchmarkGetAlbumByIDExists	10.9 µs	77.6 µs	-85.89%
❌	BenchmarkGetAlbumByIDNotFound	10.1 µs	66.8 µs	-84.81%
❌	BenchmarkGetAlbums	15.7 µs	92.5 µs	-83.01%