test(rust): cover Azure table URI separators on Windows (#3810)

## Summary
- add cross-platform regression coverage for Azure table URI
construction
- assert that az:// database paths always produce forward-slash blob
keys

## Root cause
ListingDatabase previously used the host filesystem Path join operation
for object-store URIs, which inserted a backslash on Windows. The URI
construction was corrected in #2575, but the original Azure report had
no regression coverage and remained open.

## Validation
- cargo fmt --all
- cargo test --quiet --features remote -p lancedb
test_table_uri_uses_forward_slashes_for_azure
- cargo check --quiet --features remote --tests --examples
- cargo clippy --quiet --features remote --tests --examples

Fixes #2283

<!-- lance-gatekeeper-fix:v1 agent=dd96adfd0fcf303c11e873300663d8f6
generation=1 -->

Co-authored-by: Gatefixer <313497061+lancedb-gatefixer[bot]@users.noreply.github.com>

rust/lancedb/src/database/listing.rs

@@ -2569,6 +2569,21 @@ mod tests {
         }
     }
 
+    /// Regression test for https://github.com/lancedb/lancedb/issues/2283.
+    ///
+    /// Object-store URIs must use `/` on every platform. In particular, joining
+    /// with `std::path::Path` used to insert a `\\` into Azure blob keys on
+    /// Windows.
+    #[tokio::test]
+    async fn test_table_uri_uses_forward_slashes_for_azure() {
+        let (_tempdir, mut db) = setup_database().await;
+        db.uri = "az://test/db/test".to_string();
+
+        let uri = db.table_uri("test").unwrap();
+
+        assert_eq!(uri, "az://test/db/test/test.lance");
+    }
+
     /// Regression: connecting via a URL-style URI (which goes through
     /// `url::Url::parse` and the `query_pairs_mut()` path) must not
     /// append a trailing `?` to per-table URIs when the input URI has