Let the admin choose one of eight colour profiles

Indigo (the default), Blue, Teal, Green, Amber, Rose and Violet in the
Vibrant style and Graphite in the Neutral style are generated from
config into the stylesheet. Admin settings opens with a colour profile
card: a swatch previews the profile on the page, and Save Settings
stores it as color_profile, which AppServiceProvider hands to the
package's resolver, so every page, mail and error page wears it. An
unknown profile is refused, and a saved one that disappears falls back
to indigo.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V9NnLxnPp8vaaurb3Z1MFy

website/index.html

@@ -253,7 +253,7 @@
             <article class="feature">
                 <span class="badge-icon badge-icon--tertiary" aria-hidden="true"><svg viewBox="0 0 100 100"><use href="#s-cookie-6"/></svg><svg class="icon" aria-hidden="true"><use href="#i-palette"/></svg></span>
                 <h3>Your branding</h3>
-                <p>Your logo, site title and description on the upload page.</p>
+                <p>Your logo, site title and description on the upload page, in one of eight colour profiles.</p>
             </article>
             <article class="feature">
                 <span class="badge-icon" aria-hidden="true"><svg viewBox="0 0 100 100"><use href="#s-cookie-6"/></svg><svg class="icon" aria-hidden="true"><use href="#i-shield-lock"/></svg></span>