Banner style is no longer a generated file, public page gets appearance as CSS variables. Fixes #13

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

src/backend/data.rs

@@ -741,14 +741,29 @@ pub struct Appearance {
     id: i32,
     pub banner: Option<String>,
     pub text: Option<String>,
-    pub title: Option<String>,
-    pub css_name: Option<String>
+    pub title: Option<String>
 }
 
 impl Appearance {
     pub fn id(&self) -> i32 {
         self.id
     }
+
+    /// CSS variables for the banner of the public page, used as its `style` attribute.
+    /// The styles themselves are in `assets/css/public.css`.
+    pub fn banner_style(&self) -> String {
+        match &self.banner {
+            Some(banner) if is_css_safe_file_name(banner) => format!("--rz-banner-image: url('/data/{}')", banner),
+            _ => String::new()
+        }
+    }
+}
+
+/// The value is put into a `style` attribute, so it must not be able to end the `url()` or the declaration
+fn is_css_safe_file_name(name: &str) -> bool {
+    !name.is_empty()
+        && !name.starts_with('.')
+        && name.chars().all(|c| c.is_ascii_alphanumeric() || c == '-' || c == '_' || c == '.')
 }
 
 pub fn validate_closing_time(time: &ClosingTime) -> Result<(), ValidationError> {
@@ -1272,6 +1287,25 @@ mod tests {
         assert_eq!(SlotType::Day.to_string(), "Day");
     }
 
+    #[test]
+    fn banner_style_sets_image_variable() {
+        let appearance = Appearance { banner: Some("my-banner_1.jpg".to_string()), ..Default::default() };
+        assert_eq!(appearance.banner_style(), "--rz-banner-image: url('/data/my-banner_1.jpg')");
+    }
+
+    #[test]
+    fn banner_style_is_empty_without_banner() {
+        assert_eq!(Appearance::default().banner_style(), "");
+    }
+
+    #[test]
+    fn banner_style_ignores_unsafe_file_names() {
+        for name in ["", "a'); color: red; x: url('.jpg", "a b.jpg", "../config.toml", "a/b.jpg", "a\\b.jpg", "a\"b.jpg", "a;b.jpg", "a)b.jpg", ".hidden"] {
+            let appearance = Appearance { banner: Some(name.to_string()), ..Default::default() };
+            assert_eq!(appearance.banner_style(), "", "name: {:?}", name);
+        }
+    }
+
     #[test]
     fn enum_defaults() {
         assert_eq!(ReservationState::default(), ReservationState::New);