ps1: embed real game art (ICON0 + PIC1) in converted EBOOTs

Fetch the game's cover art (libretro / ScreenScraper / IGDB / Wikipedia,
reusing the local cover cache) and bake it into the EBOOT's ICON0 (144x80
XMB icon) and PIC1 (480x272 launch background) instead of the default PS1
icon. Best-effort: falls back to the base icon/empty background when no art
is found. convert()/convert_to_folder() gain optional icon0/pic1 params.

app/ps1_convert.py

@@ -871,6 +871,8 @@ def convert(
     progress_cb=None,
     cancel_event=None,
     complevel: int = 1,
+    icon0: Optional[bytes] = None,
+    pic1: Optional[bytes] = None,
 ) -> Path:
     """Convert a PS1 disc image to ``out_path`` (an ``EBOOT.PBP``).
 
@@ -878,6 +880,9 @@ def convert(
     ``.iso``/``.img``/``.bin``. ``base_pbp`` must be a PSN PS1 classic EBOOT.
     ``complevel`` is the DEFLATE level for the disc data (1-9; 0 = raw, which
     does not boot on real hardware and is only useful for diagnostics).
+    ``icon0`` (144x80 PNG) and ``pic1`` (480x272 PNG) override the generated
+    icon/background; when absent the base PBP's ICON0 is reused and PIC1 is
+    left empty.
     """
     if not base_pbp.is_file():
         raise ConversionError(f"base.pbp not found: {base_pbp}")
@@ -901,11 +906,10 @@ def convert(
     # Reuse the base PBP's SFO, patched with our title + game id (the
     # popstation approach), rather than rebuilding it from scratch.
     sfo = patch_sfo(extract_sfo(base_pbp), title, game_id)
-    # Reuse the base PBP's ICON0 too. The XMB icon parser is picky about PNG
-    # variants, and the base icon is guaranteed to decode; the other image
-    # sections are left empty exactly like popstation when no assets are
-    # supplied alongside the conversion.
-    icon0 = extract_icon0(base_pbp)
+    # Reuse the base PBP's ICON0 when no custom icon was supplied (the XMB
+    # icon parser is picky about PNG variants, and the base icon is guaranteed
+    # to decode). PIC1 is the launch background; empty when no art is given.
+    icon0 = icon0 or extract_icon0(base_pbp)
 
     # Sections in header order; empty sections keep the previous offset.
     sections = {
@@ -913,7 +917,7 @@ def convert(
         "icon0": icon0,
         "icon1": b"",
         "pic0": b"",
-        "pic1": b"",
+        "pic1": pic1 or b"",
         "snd0": b"",
         "data_psp": data_psp,
         # psar written separately, sized after everything else.
@@ -981,6 +985,8 @@ def convert_to_folder(
     progress_cb=None,
     cancel_event=None,
     complevel: int = 1,
+    icon0: Optional[bytes] = None,
+    pic1: Optional[bytes] = None,
 ) -> Path:
     """Convert a PS1 disc into a game folder ready for /PSP/GAME.
 
@@ -993,7 +999,8 @@ def convert_to_folder(
     folder.mkdir(parents=True, exist_ok=True)
 
     convert(source, title, game_id, base_pbp, folder / "EBOOT.PBP",
-            progress_cb=progress_cb, cancel_event=cancel_event, complevel=complevel)
+            progress_cb=progress_cb, cancel_event=cancel_event, complevel=complevel,
+            icon0=icon0, pic1=pic1)
     return folder