Added customizable colours of the public page with palettes and live preview. Fixes #14

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/backend/data.rs

@@ -4,6 +4,7 @@ use std::fmt::{Display, Formatter};
 use std::str::FromStr;
 use chrono::{Local, NaiveDate, NaiveTime, Weekday};
 use lazy_static::lazy_static;
+use crate::backend::color::Colors;
 use regex::Regex;
 use rust_decimal::Decimal;
 use serde::{Deserialize, Serialize};
@@ -741,7 +742,11 @@ pub struct Appearance {
     id: i32,
     pub banner: Option<String>,
     pub text: Option<String>,
-    pub title: Option<String>
+    pub title: Option<String>,
+    // Forms that edit the title or the text don't send the colours
+    #[serde(default)]
+    #[cfg_attr(feature = "ssr", sqlx(flatten))]
+    pub colors: Colors
 }
 
 impl Appearance {