feat: add batch upload, CLI, and exception hierarchy

- Add RbxError base class with AuthError, RateLimitError, UploadError,
  and AssetNotFoundError subclasses
- Add BatchUploadItem and BatchResult dataclasses
- Add batch_upload method with semaphore-limited concurrency (2 at a time)
- Add configurable max_attempts and poll_interval to upload_clothing_image
- Add CLI with upload and onsale commands (rbx-upload[cli] extra)
- Improve auth error handling across all client methods
- Bump version to 0.2.0

README.md

@@ -8,6 +8,12 @@ Async Python client for (re)uploading and managing Roblox assets.
 uv add rbx-upload
 ```
 
+With CLI support:
+
+```bash
+uv add "rbx-upload[cli]"
+```
+
 ## Usage
 
 ```python
@@ -43,17 +49,82 @@ async with RobloxClient(
     )
 ```
 
+### Batch upload
+
+```python
+from rbx_upload import RobloxClient, RbxAssetType, BatchUploadItem
+
+items = [
+    BatchUploadItem(image=img1, name="Shirt A", asset_type=RbxAssetType.SHIRT, group_id=67890),
+    BatchUploadItem(image=img2, name="Shirt B", asset_type=RbxAssetType.SHIRT, group_id=67890),
+    BatchUploadItem(image=img3, name="Pants A", asset_type=RbxAssetType.PANTS, group_id=67890),
+]
+
+async with RobloxClient(roblosecurity="...", publisher_user_id=12345) as client:
+    result = await client.batch_upload(items)
+
+    for item, upload in result.succeeded:
+        print(f"{item.name}: asset_id={upload['asset_id']}")
+
+    for item, error in result.failed:
+        print(f"{item.name} failed: {error}")
+```
+
+### Error handling
+
+```python
+from rbx_upload import AuthError, RateLimitError, UploadError, AssetNotFoundError
+
+try:
+    result = await client.upload_clothing_image(...)
+except AuthError:
+    # Invalid or expired ROBLOSECURITY token
+    ...
+except RateLimitError:
+    # Hit rate limit, back off and retry
+    ...
+except UploadError:
+    # Upload operation timed out or failed
+    ...
+```
+
+## CLI
+
+Requires `pip install "rbx-upload[cli]"`. Set `ROBLOSECURITY` in your environment.
+
+```bash
+# Upload a clothing image
+rbx-upload upload shirt.png --name "My Shirt" --group 67890 --publisher 12345
+
+# Put an asset on sale
+rbx-upload onsale 123456789 --name "My Shirt" --group 67890 --publisher 12345 --price 10
+```
+
+Run `rbx-upload --help` or `rbx-upload <command> --help` for all options.
+
 ## API
 
 ### `RobloxClient(roblosecurity, publisher_user_id, proxy=None)`
 
-All methods are async
+All methods are async.
 
 | Method | Description |
 |---|---|
 | `asset_from_id(asset_id)` | Fetch asset info. Returns `ClothingAsset` for shirts/pants, `RbxAsset` otherwise. |
 | `fetch_clothing_image(asset)` | Fetch raw PNG bytes for a clothing asset. |
-| `upload_clothing_image(image, name, description, asset_type, group_id)` | Upload a clothing image. Returns `{"asset_id": int}`. |
+| `upload_clothing_image(image, name, description, asset_type, group_id, max_attempts=10, poll_interval=1.0)` | Upload a clothing image. Returns `{"asset_id": int}`. |
+| `batch_upload(items, max_attempts=10, poll_interval=1.0)` | Upload multiple items (2 at a time). Returns `BatchResult`. |
 | `onsale_asset(asset_id, name, description, group_id, price=5)` | Put an asset on sale. |
 
-`proxy` replaces `roblox.com` in all URLs
+`proxy` replaces `roblox.com` in all URLs.
+
+### Exceptions
+
+All exceptions inherit from `RbxError`.
+
+| Exception | When raised |
+|---|---|
+| `AuthError` | Invalid/expired token or not authorized |
+| `RateLimitError` | HTTP 429 from Roblox |
+| `UploadError` | Upload operation timed out |
+| `AssetNotFoundError` | Asset ID does not exist |