Update Match3D/image-generation docs & code

Adds/updates documentation, assets and implementation for Match3D and puzzle image generation workflows. Key changes: decision logs and pitfalls updated to prefer VectorEngine Gemini for Match3D material sheets and to require edits (multipart) for 1:1 container reference images; guidance added for when to use APIMart vs VectorEngine. .env.example clarified APIMart/Responses config. Many new public assets and PPT visuals added. Code changes across frontend and backend: updated shared contracts, server-rs match3d/puzzle/image-generation handlers, VectorEngine/OpenAI image generation clients, and multiple React components/tests to handle UI/background/container image signing, edits workflow, and puzzle UI background resolution. Added src/services/puzzle-runtime/puzzleUiBackgroundSource.ts and related test updates. Includes notes about multipart HTTP/1.1 requirement and test/verification commands in docs.

server-rs/crates/api-server/src/app.rs

@@ -90,12 +90,13 @@ use crate::{
     match3d::{
         click_match3d_item, compile_match3d_agent_draft, create_match3d_agent_session,
         delete_match3d_work, execute_match3d_agent_action, finish_match3d_time_up,
-        generate_match3d_background_image_for_work, generate_match3d_cover_image,
-        generate_match3d_item_assets_for_work, generate_match3d_work_tags,
-        get_match3d_agent_session, get_match3d_run, get_match3d_work_detail, get_match3d_works,
-        list_match3d_gallery, persist_match3d_generated_model, publish_match3d_work,
-        put_match3d_audio_assets, put_match3d_work, restart_match3d_run, start_match3d_run,
-        stop_match3d_run, stream_match3d_agent_message, submit_match3d_agent_message,
+        generate_match3d_background_image_for_work, generate_match3d_container_image_for_work,
+        generate_match3d_cover_image, generate_match3d_item_assets_for_work,
+        generate_match3d_work_tags, get_match3d_agent_session, get_match3d_run,
+        get_match3d_work_detail, get_match3d_works, list_match3d_gallery,
+        persist_match3d_generated_model, publish_match3d_work, put_match3d_audio_assets,
+        put_match3d_work, restart_match3d_run, start_match3d_run, stop_match3d_run,
+        stream_match3d_agent_message, submit_match3d_agent_message,
     },
     password_entry::password_entry,
     password_management::{change_password, reset_password},
@@ -969,10 +970,15 @@ pub fn build_router(state: AppState) -> Router {
         )
         .route(
             "/api/creation/match3d/works/{profile_id}/cover-image",
-            post(generate_match3d_cover_image).route_layer(middleware::from_fn_with_state(
-                state.clone(),
-                require_bearer_auth,
-            )),
+            post(generate_match3d_cover_image)
+                // 中文注释：抓大鹅封面支持上传主图与多张参考图，沿用拼图参考图入口上限。
+                .layer(DefaultBodyLimit::max(
+                    PUZZLE_REFERENCE_IMAGE_BODY_LIMIT_BYTES,
+                ))
+                .route_layer(middleware::from_fn_with_state(
+                    state.clone(),
+                    require_bearer_auth,
+                )),
         )
         .route(
             "/api/creation/match3d/works/{profile_id}/background-image",
@@ -980,6 +986,12 @@ pub fn build_router(state: AppState) -> Router {
                 middleware::from_fn_with_state(state.clone(), require_bearer_auth),
             ),
         )
+        .route(
+            "/api/creation/match3d/works/{profile_id}/container-image",
+            post(generate_match3d_container_image_for_work).route_layer(
+                middleware::from_fn_with_state(state.clone(), require_bearer_auth),
+            ),
+        )
         .route(
             "/api/creation/match3d/works/{profile_id}/item-assets",
             post(generate_match3d_item_assets_for_work).route_layer(