fix(thumbnails): gate the preview fallback past the cap, and History outputs (#543)

The gate's OVER branch looked its source up by name and served it without the
trash check. A History output recorded inside a trash folder now answers missing.

py/api/history_current.py

@@ -17,6 +17,7 @@ from aiohttp import web
 
 from . import thumbnail_settings
 from .images import _canonical, _public_path, SERVABLE_EXTENSIONS, VIDEO_EXTENSIONS
+from .images import in_trash_below_roots
 from .images import existing_media_thumbnail, media_thumbnail_rel
 
 try:
@@ -248,6 +249,9 @@ def _open_current_target(
     A *preview* (a file under ``thumbnails/``) may also be JPEG XL (#317)."""
     if _canonical(target) != target:
         raise CurrentLocationUnavailable("not_authorized", stale=True)
+    if in_trash_below_roots(target, [namespace]):
+        # An output recorded before #501 skipped trash folders (#543).
+        raise CurrentLocationUnavailable("missing")
     if not _authorized(target, namespace, scope):
         raise CurrentLocationUnavailable("not_authorized")
     suffix = target.suffix.lower()

py/api/thumbnail_auto.py

@@ -225,6 +225,8 @@ def _quick_source(root, parts):
         for name in (base + extension, base + extension.upper()):
             path = folder / name
             if _regular_file(path) and _is_within(path, root):
+                if in_trash_below_roots(path, [root]):
+                    return None  # also the fallback past the gate's cap (#543)
                 return path, extension in VIDEO_EXTENSIONS
     return None