feat: polish jump hop themed runtime assets

server-rs/crates/spacetime-module/src/jump_hop/tables.rs

@@ -59,6 +59,9 @@ pub struct JumpHopWorkProfileRow {
     // 跳一跳生成主题独立于作品标题；旧行按 work_title 兜底。
     #[default(None::<String>)]
     pub(crate) theme_text: Option<String>,
+    // 跳一跳左上角真实可点击返回按钮的独立透明资产快照；旧行为空时运行态使用样式兜底。
+    #[default(None::<String>)]
+    pub(crate) back_button_asset_json: Option<String>,
 }
 
 #[spacetimedb::table(

server-rs/crates/spacetime-module/src/jump_hop/types.rs

@@ -56,6 +56,7 @@ pub struct JumpHopDraftCompileInput {
     pub tile_atlas_asset_json: Option<String>,
     pub tile_assets_json: Option<String>,
     pub cover_composite: Option<String>,
+    pub back_button_asset_json: Option<String>,
     pub generation_status: Option<String>,
     pub compiled_at_micros: i64,
 }
@@ -248,6 +249,7 @@ pub struct JumpHopDraftSnapshot {
     pub tile_assets: Vec<JumpHopTileAssetSnapshot>,
     pub path: Option<module_jump_hop::JumpHopPath>,
     pub cover_composite: Option<String>,
+    pub back_button_asset: Option<JumpHopCharacterAssetSnapshot>,
     pub generation_status: String,
 }
 
@@ -291,6 +293,7 @@ pub struct JumpHopWorkSnapshot {
     pub path: module_jump_hop::JumpHopPath,
     pub cover_image_src: String,
     pub cover_composite: Option<String>,
+    pub back_button_asset: Option<JumpHopCharacterAssetSnapshot>,
     pub publication_status: String,
     pub publish_ready: bool,
     pub play_count: u32,