Add file size conversion and enhance Civitai job processing

- Introduced the `file_size_bytes` function to convert Civitai model sizes from kilobytes to bytes, improving data handling.
- Updated the `seed_civitai` function to include file size in job definitions, enhancing model processing efficiency.
- Enhanced the `should_skip` function to utilize expected size for faster decision-making during job processing.
- Added tests for new functionality, ensuring robustness in file size handling and job processing logic.

src/gpu_rent/civitai.py

@@ -80,6 +80,19 @@ def pick_primary_file(version: dict) -> dict | None:
     return None
 
 
+def file_size_bytes(info: dict) -> int | None:
+    """Civitai ``sizeKB`` (float) → bytes, or None."""
+    raw = info.get("sizeKB")
+    if raw is None:
+        raw = info.get("sizeKb")
+    if raw is None:
+        return None
+    try:
+        return int(round(float(raw) * 1024.0))
+    except (TypeError, ValueError):
+        return None
+
+
 def pick_preview_image(version: dict) -> tuple[str, str] | None:
     """First usable Civitai preview → (url, sidecar_suffix) for SwarmUI.