Added guide for configuration of banner.

docs/guides/administration/.pages

@@ -9,6 +9,7 @@ nav:
   - configuring-internal-ca.md
   - configuring-http-proxy.md
   - configuring-timezone.md
+  - configuring-banner.md
   - configuring-vulnerability-sources.md
   - running-air-gapped.md
   - configuring-observability.md

docs/guides/administration/configuring-banner.md

@@ -0,0 +1,114 @@
+# Configuring the banner
+
+Dependency-Track supports a configurable, application-wide banner that is
+displayed at the top of the application for all authenticated users.
+This guide covers how administrators enable, style, and manage the banner.
+
+## Overview
+
+The banner is intended for short, system-wide announcements, for example
+planned maintenance windows or important notices. It is shown to authenticated
+users only and does not appear on the login or change-password pages.
+
+The banner is configured entirely from the administration UI under
+**Administration → Configuration → Banner** (route `/admin/configuration/banner`).
+
+!!! note
+    Access to the banner configuration requires the `SYSTEM_CONFIGURATION`
+    permission.
+
+## Settings
+
+The configuration screen exposes the following controls:
+
+| Setting | Description |
+| --- | --- |
+| **Activate banner** | Master on/off switch. When disabled, no banner is shown. |
+| **Allow users to dismiss banner** | Adds a close (×) button so users can hide the banner. See [Dismissing the banner](#dismissing-the-banner). |
+| **Message** | Plain-text content of the banner ([default mode](#default-mode)). |
+| **Color scheme** | Preset color of the banner ([default mode](#default-mode)). |
+| **Custom mode** | Switches to an HTML editor instead of message + color scheme. |
+| **HTML content** | Raw HTML rendered as the banner ([custom mode](#custom-mode)). |
+
+The banner content can be defined in one of two modes: the [default](#default-mode)
+text-and-color mode, or the [custom](#custom-mode) HTML mode.
+
+## Modes
+
+### Default mode
+
+The default mode renders a plain-text **Message** using one of the preset
+**Color schemes**. This is the recommended option for most announcements.
+
+The following color schemes are available:
+
+* `red`
+* `orange`
+* `green`
+* `blue`
+* `lilac`
+
+To configure a banner in default mode:
+
+1. Enable **Activate banner**.
+2. Enable **Allow users to dismiss banner** if users should be able to close it.
+3. Enter the banner text in the **Message** field.
+4. Select a **Color scheme**.
+5. Leave **Custom mode** disabled.
+6. Select **Update** to save.
+
+!!! note
+    The **Update** button remains disabled while the banner is active and the
+    **Message** field is empty.
+
+The screenshot below shows a banner configured in **default mode** with
+**Allow users to dismiss banner** enabled:
+
+![Banner configured in default mode with dismiss enabled](../../assets/images/guides/administration/configuring-banner/default_banner_example.png)
+
+### Custom mode
+
+Custom mode replaces the message and color scheme with a full HTML editor,
+giving complete control over the banner's styling, layout, and links.
+Use this mode when the preset color schemes or plain text are not sufficient,
+for example to embed a link.
+
+To configure a banner in custom mode:
+
+1. Enable **Activate banner**.
+2. Enable **Allow users to dismiss banner** if users should be able to close it.
+3. Enable **Custom mode**. This clears the message and color settings and seeds
+   the editor with an example template.
+4. Edit the **HTML content** in the editor.
+5. Select **Update** to save.
+
+!!! note
+    When custom mode is enabled, the **Message** field and color swatches are
+    disabled. The **Update** button remains disabled while the banner is active
+    and the **HTML content** is empty.
+
+??? example "Example HTML content"
+    ```html linenums="1"
+    <div style="background:#321FDB;color:#fff;padding:0.5rem 1rem;border-bottom:1px solid rgba(0,0,0,.2);font-size:1rem;line-height:1.5;text-align:center">
+      <strong>Example:</strong> <span>Your HTML-Banner Text</span>
+    </div>
+    ```
+
+The screenshot below shows a banner configured in **custom mode** with
+**Allow users to dismiss banner** enabled:
+
+![Banner configured in custom mode with dismiss enabled](../../assets/images/guides/administration/configuring-banner/custom_banner_example.png)
+
+## Dismissing the banner
+
+The **Allow users to dismiss banner** option controls whether users can hide the
+banner themselves.
+
+When enabled:
+
+* A close (×) button is shown in the top-right corner of the banner.
+* When a user closes the banner, it stays hidden for the remainder of their
+  browser session.
+* The banner reappears in a new login session.
+
+When disabled, no close button is shown and users cannot hide the banner.