feat: Eliminate CGO dependency by switching to pure Go SQLite

Replaced github.com/mattn/go-sqlite3 (CGO-based) with modernc.org/sqlite
(pure Go implementation) to enable CGO-free builds while maintaining
full SQLite functionality.

Benefits:
- ✅ Cross-compilation without C compiler requirements
- ✅ Simplified build environment (no CGO_ENABLED=1)
- ✅ Reduced deployment dependencies
- ✅ Easier container builds and static linking
- ✅ Full SQLite compatibility maintained

Changes:
- Updated go.mod to use modernc.org/sqlite v1.34.4
- Updated database import to use pure Go SQLite driver
- Removed CGO_ENABLED=1 from all Makefile build targets
- Verified all binaries (skyview, beast-dump, skyview-data) build successfully

The modernc.org/sqlite package is a cgo-free port of SQLite that transpiles
the original C code to Go, providing identical functionality without CGO.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

internal/database/database.go

@@ -14,7 +14,7 @@ import (
 	"fmt"
 	"time"
 
-	_ "github.com/mattn/go-sqlite3" // SQLite driver
+	_ "modernc.org/sqlite" // Pure Go SQLite driver (CGO-free)
 )
 
 // Database represents the main database connection and operations