feat(web): choose where the search sits, and controls no longer select text

- settings get a search position (left, center by default, right); the top bar
  is three zones and the suggestions open towards the free space
- buttons, chips, tabs, menu items and the home screen controls are not
  text-selectable, so clicks and double clicks no longer highlight labels

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

services/api/internal/auth/validate.go

@@ -86,10 +86,11 @@ var commonPasswords = func() map[string]struct{} {
 }()
 
 var uiPrefEnums = map[string][]string{
-	"theme":         {"dark", "light", "system"},
-	"wave_variant":  {"orb", "liquid"},
-	"web_player":    {"bar", "island"},
-	"mobile_player": {"cover", "wave"},
+	"theme":           {"dark", "light", "system"},
+	"wave_variant":    {"orb", "liquid"},
+	"web_player":      {"bar", "island"},
+	"search_position": {"center", "left", "right"},
+	"mobile_player":   {"cover", "wave"},
 }
 
 // ValidateUIPrefs проверяет значения перечислений и диапазон кроссфейда.
@@ -107,6 +108,7 @@ func ValidateUIPrefs(p UIPrefs) error {
 	}
 	for name, v := range map[string]*string{
 		"theme": p.Theme, "wave_variant": p.WaveVariant, "web_player": p.WebPlayer, "mobile_player": p.MobilePlayer,
+		"search_position": p.SearchPos,
 	} {
 		if err := check(name, v); err != nil {
 			return err
@@ -130,6 +132,9 @@ func MergeUIPrefs(base, patch UIPrefs) UIPrefs {
 	if patch.WebPlayer != nil {
 		base.WebPlayer = patch.WebPlayer
 	}
+	if patch.SearchPos != nil {
+		base.SearchPos = patch.SearchPos
+	}
 	if patch.MobilePlayer != nil {
 		base.MobilePlayer = patch.MobilePlayer
 	}