feat(search): filter tag results by colour

Pass the active colour filter through tag searches and apply the existing palette match inside the tag query and count paths.

Update the UI Lab mock backend so colour filtering behaves the same way when testing tag search results.

src-tauri/src/commands.rs

@@ -162,6 +162,8 @@ pub struct TagSearchParams {
     pub media_kind: Option<String>,
     pub favorites_only: Option<bool>,
     pub rating_min: Option<i64>,
+    /// Optional `[r, g, b]` color filter applied within the tag result set.
+    pub color: Option<[u8; 3]>,
     pub limit: Option<usize>,
     pub offset: Option<usize>,
 }
@@ -957,6 +959,7 @@ pub async fn search_images_by_tag(
     let conn = db.get().map_err(|e| e.to_string())?;
     let limit = params.limit.unwrap_or(64);
     let offset = params.offset.unwrap_or(0);
+    let color = params.color.map(|[r, g, b]| (r, g, b));
     let (images, total) = db::search_images_by_tag(
         &conn,
         &params.query,
@@ -964,6 +967,7 @@ pub async fn search_images_by_tag(
         params.media_kind.as_deref(),
         params.favorites_only.unwrap_or(false),
         params.rating_min.unwrap_or(0),
+        color,
         limit,
         offset,
     )