[Bug]: HTTP SDK match_sparse crashes when sparse_data is a dict (AttributeError: 'dict' object has no attribute 'to_dict')

## Problem

`match_sparse` is declared to accept `SparseVector | dict`:

```python
def match_sparse(self, vector_column_name: str, sparse_data: SparseVector | dict, ...)
```

and both other SDKs honor that - the embedded SDK has an explicit `case dict()` arm and the thrift SDK handles dicts in `make_match_sparse_expr`. But the HTTP client crashes before sending anything:

```python
table.output(["c1"]).match_sparse("c2", {0: 1.0, 20: 2.0}, "ip", 3)
# AttributeError: 'dict' object has no attribute 'to_dict'
```

## Root cause

`python/infinity_sdk/infinity/infinity_http.py`, `table_http_result.match_sparse()`:

```python
"query_vector": sparse_data.to_dict(), # assumes SparseVector unconditionally
```

## Fix

Convert a `SparseVector` with `to_dict()` and pass a `dict` through as-is (the server parses `query_vector` as an `{index: value}` JSON object, which is exactly what a plain dict serializes to). Empty dicts and other types raise a clear `InfinityException` instead of an `AttributeError`.

## Testing

- Reproduced on current main (eca7266): dict input raised `AttributeError`; after the fix the same dict builds a `query_vector` payload identical in shape to the one `SparseVector.to_dict()` produces, `SparseVector` input is unchanged, and a list / empty dict raise `InfinityException`.
- Added regression test `test_sparse_knn_with_dict` in `python/test_pysdk/test_knn.py`, mirroring `test_sparse_knn` with a dict argument and the same expected result.
- Full pysdk suite not run locally; it needs a running server.

Start in python/infinity_sdk/infinity/infinity_http.py at table_http_result.match_sparse(), then inspect python/test_pysdk/test_knn.py and the existing test_sparse_knn case. Verify dict and SparseVector inputs produce the expected query_vector payload, while a list and empty dict raise InfinityException; run the focused test if a server is available.

Written by the indexing model from the issue text.