fix: show unsaved F95 covers and clarify import results

backend/app/routers/metadata.py

@@ -1,3 +1,4 @@
+import base64
 from urllib.parse import quote
 
 from fastapi import APIRouter, HTTPException, status
@@ -6,6 +7,7 @@ from pydantic import BaseModel, SecretStr
 from starlette.concurrency import run_in_threadpool
 
 from app import f95
+from app.blobs import read_bytes
 from app.deps import DB, CurrentUser, has_perm
 from app.f95_session import open_session, seal
 from app.routers.games import make_cover
@@ -31,6 +33,7 @@ class MetaOut(BaseModel):
     description: str = ""
     tags: list[str] = []
     cover_hash: str | None = None
+    cover_preview: str | None = None
     cover_warning: str | None = None
     auth_required: bool = False
     metadata_available: bool = True
@@ -47,6 +50,9 @@ def load_metadata(url: str, cookie: str = "", user_agent: str = "") -> dict:
     if image := metadata.pop("image_url", None):
         try:
             metadata["cover_hash"] = make_cover(f95.fetch_image(image, metadata["url"], cookie, user_agent))
+            # Unsaved covers cannot be read through the protected /blobs route yet.
+            metadata["cover_preview"] = "data:image/webp;base64," + base64.b64encode(
+                read_bytes(metadata["cover_hash"])).decode("ascii")
         except f95.F95AuthError as e:
             metadata["auth_required"] = True
             metadata["cover_warning"] = f"{e}. Остальные данные загружены."