Fix bugs, convert thumbnail to png, add context menu

backend/app/models/document.py

@@ -38,6 +38,18 @@ class Document(Base):
     updated_at: Mapped[str] = mapped_column(Text, default=_now_iso, onupdate=_now_iso)
     deleted_at: Mapped[str | None] = mapped_column(Text, nullable=True, default=None)
 
+    @property
+    def in_trash(self) -> bool:
+        return self.deleted_at is not None
+
+    @property
+    def filename(self) -> str:
+        return self.original_filename
+
+    @property
+    def mime_type(self) -> str:
+        return "application/pdf"
+
     # Relationships
     annotation_state: Mapped["AnnotationState"] = relationship(
         "AnnotationState",