feat: add user reset-apikey command

Adds `hf user reset-apikey <username>` to regenerate a user API key.
Requires user.manage permission. Returns the new key (shown once only).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/commands/user.go

@@ -390,3 +390,45 @@ func RunUserDelete(username, tokenFlag string) {
 	}
 	fmt.Printf("user deleted: %s\n", username)
 }
+
+// resetAPIKeyResponse matches the backend reset-apikey response.
+type resetAPIKeyResponse struct {
+	UserID   int    `json:"user_id"`
+	Username string `json:"username"`
+	APIKey   string `json:"api_key"`
+	Message  string `json:"message"`
+}
+
+// RunUserResetAPIKey implements `hf user reset-apikey <username>`.
+func RunUserResetAPIKey(username, tokenFlag string) {
+	token := ResolveToken(tokenFlag)
+	cfg, err := config.Load()
+	if err != nil {
+		output.Errorf("config error: %v", err)
+	}
+	c := client.New(cfg.BaseURL, token)
+	data, err := c.Post("/users/"+username+"/reset-apikey", nil)
+	if err != nil {
+		output.Errorf("failed to reset API key: %v", err)
+	}
+
+	if output.JSONMode {
+		var raw json.RawMessage
+		if err := json.Unmarshal(data, &raw); err != nil {
+			output.Errorf("invalid JSON response: %v", err)
+		}
+		output.PrintJSON(raw)
+		return
+	}
+
+	var r resetAPIKeyResponse
+	if err := json.Unmarshal(data, &r); err != nil {
+		fmt.Printf("API key reset for: %s\n", username)
+		return
+	}
+	output.PrintKeyValue(
+		"username", r.Username,
+		"api-key", r.APIKey,
+		"message", r.Message,
+	)
+}