Add support for "from_name" field in email notifications

Introduced a new optional "from_name" attribute to email settings, allowing customization of the sender's display name in outgoing emails. Updated backend models, APIs, and front-end components to include and handle this field properly. This enhances email clarity and personalization for users.

frontend/src/pages/AdminUsersPage.jsx

@@ -13,6 +13,7 @@ export function AdminUsersPage() {
     smtp_username: "",
     smtp_password: "",
     clear_smtp_password: false,
+    from_name: "",
     from_email: "",
     use_starttls: true,
     use_ssl: false,
@@ -37,6 +38,7 @@ export function AdminUsersPage() {
       smtp_username: smtp.smtp_username || "",
       smtp_password: "",
       clear_smtp_password: false,
+      from_name: smtp.from_name || "",
       from_email: smtp.from_email || "",
       use_starttls: !!smtp.use_starttls,
       use_ssl: !!smtp.use_ssl,
@@ -85,6 +87,7 @@ export function AdminUsersPage() {
         ...emailSettings,
         smtp_host: emailSettings.smtp_host.trim() || null,
         smtp_username: emailSettings.smtp_username.trim() || null,
+        from_name: emailSettings.from_name.trim() || null,
         from_email: emailSettings.from_email.trim() || null,
         smtp_password: emailSettings.smtp_password || null,
         alert_recipients: recipients,
@@ -249,6 +252,14 @@ export function AdminUsersPage() {
             />
           </div>
 
+          <div className="admin-field">
+            <label>From name</label>
+            <input
+              value={emailSettings.from_name}
+              placeholder="NexaPG Alerts"
+              onChange={(e) => setEmailSettings({ ...emailSettings, from_name: e.target.value })}
+            />
+          </div>
           <div className="admin-field">
             <label>From email</label>
             <input