Refactor database interface to use *sql.DB directly

Simplified the database layer by removing custom interface wrappers
and using standard library *sql.DB and *sql.Tx types directly.

Changes:
- Removed DBConnection and DBTransaction interfaces from database.go
- Removed NewDBConnection() wrapper function
- Updated TokenGenerator to use *sql.DB instead of DBConnection
- Updated all validation and revocation methods to accept *sql.Tx
- Updated TableManager to work with *sql.DB directly
- Updated all tests to use db.Begin() instead of custom wrappers
- Fixed GeneratorConfig.DB field (was DBConn)
- Updated documentation in doc.go with correct API usage

Benefits:
- Simpler API with fewer abstractions
- Works directly with database/sql standard library
- Compatible with GORM (via gormDB.DB()) and Bun (share same *sql.DB)
- Easier to understand and maintain
- No unnecessary wrapper layers

Breaking changes:
- GeneratorConfig.DBConn renamed to GeneratorConfig.DB
- Removed NewDBConnection() function - pass *sql.DB directly
- ValidateAccess/ValidateRefresh now accept *sql.Tx instead of DBTransaction
- Token.Revoke/CheckNotRevoked now accept *sql.Tx instead of DBTransaction

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

hws/go.mod

@@ -3,12 +3,22 @@ module git.haelnorr.com/h/golib/hws
 go 1.25.5
 
 require (
+	git.haelnorr.com/h/golib/env v0.9.1
+	git.haelnorr.com/h/golib/hlog v0.9.0
 	github.com/pkg/errors v0.9.1
-	github.com/rs/zerolog v1.34.0
+	github.com/stretchr/testify v1.11.1
+	k8s.io/apimachinery v0.35.0
 )
 
 require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/go-logr/logr v1.4.3 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.19 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/rs/zerolog v1.34.0 // indirect
 	golang.org/x/sys v0.12.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+	k8s.io/klog/v2 v2.130.1 // indirect
+	k8s.io/utils v0.0.0-20251002143259-bc988d571ff4 // indirect
 )