feat(web): add i18n support with FR/EN locales and keyboard layout awareness

Add full internationalization system with React context, French/English
translations, and AZERTY/QWERTY keyboard layout support. Dashboard now
uses a tabbed layout (Tools, Notifications, Workflows). Config page exposes
language and keyboard preferences persisted via new /api/preferences endpoint.

💕 Generated with Crush

Assisted-by: GLM-5-Turbo via Crush <crush@charm.land>

internal/config/config.go

@@ -15,12 +15,14 @@ type Profile struct {
 	Email       string   `yaml:"email"`
 	Languages   []string `yaml:"languages"`
 	Preferences struct {
-		Editor        string `yaml:"editor"`
-		Shell         string `yaml:"shell"`
-		Theme         string `yaml:"theme"`
-		DefaultAI     string `yaml:"default_ai"`
-		AutoUpdate    bool   `yaml:"auto_update"`
-		CheckOnStart  bool   `yaml:"check_on_start"`
+		Editor         string `yaml:"editor"`
+		Shell          string `yaml:"shell"`
+		Theme          string `yaml:"theme"`
+		DefaultAI      string `yaml:"default_ai"`
+		AutoUpdate     bool   `yaml:"auto_update"`
+		CheckOnStart   bool   `yaml:"check_on_start"`
+		Language       string `yaml:"language"`
+		KeyboardLayout string `yaml:"keyboard_layout"`
 	} `yaml:"preferences"`
 }
 
@@ -179,6 +181,8 @@ func Default() *MuyueConfig {
 	cfg.Profile.Preferences.AutoUpdate = true
 	cfg.Profile.Preferences.CheckOnStart = true
 	cfg.Profile.Preferences.Theme = "charm"
+	cfg.Profile.Preferences.Language = "fr"
+	cfg.Profile.Preferences.KeyboardLayout = "azerty"
 
 	cfg.AI.Providers = []AIProvider{
 		{