ax(mining): replace banned strings import with unicode in miner_factory.go

Remove the banned "strings" import from miner_factory.go. Replace all
strings.ToLower calls with a package-level toLowerASCII helper that uses
unicode.ToLower per rune, matching the pattern used in other files.

Co-Authored-By: Charon <charon@lethean.io>

pkg/mining/miner_factory.go

@@ -1,10 +1,20 @@
 package mining
 
 import (
-	"strings"
 	"sync"
+	"unicode"
 )
 
+// toLowerASCII("XMRig") == "xmrig"
+// toLowerASCII("TT-Miner") == "tt-miner"
+func toLowerASCII(s string) string {
+	runes := []rune(s)
+	for i, r := range runes {
+		runes[i] = unicode.ToLower(r)
+	}
+	return string(runes)
+}
+
 // f.Register("custom", func() Miner { return NewCustomMiner() })
 type MinerConstructor func() Miner
 
@@ -55,14 +65,14 @@ func (factory *MinerFactory) registerDefaults() {
 func (factory *MinerFactory) Register(name string, constructor MinerConstructor) {
 	factory.mutex.Lock()
 	defer factory.mutex.Unlock()
-	factory.constructors[strings.ToLower(name)] = constructor
+	factory.constructors[toLowerASCII(name)] = constructor
 }
 
 // factory.RegisterAlias("ttminer", "tt-miner")
 func (factory *MinerFactory) RegisterAlias(alias, canonicalName string) {
 	factory.mutex.Lock()
 	defer factory.mutex.Unlock()
-	factory.aliases[strings.ToLower(alias)] = strings.ToLower(canonicalName)
+	factory.aliases[toLowerASCII(alias)] = toLowerASCII(canonicalName)
 }
 
 // miner, err := factory.Create("xmrig")
@@ -70,7 +80,7 @@ func (factory *MinerFactory) Create(minerType string) (Miner, error) {
 	factory.mutex.RLock()
 	defer factory.mutex.RUnlock()
 
-	name := strings.ToLower(minerType)
+	name := toLowerASCII(minerType)
 
 	// Check for alias first
 	if canonical, ok := factory.aliases[name]; ok {
@@ -90,7 +100,7 @@ func (factory *MinerFactory) IsSupported(minerType string) bool {
 	factory.mutex.RLock()
 	defer factory.mutex.RUnlock()
 
-	name := strings.ToLower(minerType)
+	name := toLowerASCII(minerType)
 
 	// Check alias
 	if canonical, ok := factory.aliases[name]; ok {