chore(deps): upgrade hotdata SDK 0.3.1 -> 0.4.0 (#171)

0.4.0 removes the datasets API/models and adds a usage API. The CLI
already dropped its datasets surface in #166, so the removal is a no-op
here and the new usage API is simply unused. No source changes needed.

Verified: `cargo build`/`clippy` clean, full suite (206) green, and a
production smoke test (auth status, databases list, an arrow-decoded
query) against workspace AgentRyan succeeds.

Co-authored-by: Eddie A Tejeda <669988+eddietejeda@users.noreply.github.com>

Author: eddietejeda

Cargo.lock

@@ -16,7 +16,7 @@ path = "src/main.rs"
 # behind a shared multi-thread tokio runtime. The `arrow` feature backs result
 # decode; `upload_stream` carries `content_length` (sized body, not chunked, so
 # the server can fast-fail an oversized upload — see src/sdk.rs::Api::upload_stream).
-hotdata = { version = "0.3.1", features = ["arrow"] }
+hotdata = { version = "0.4.0", features = ["arrow"] }
 # Shared multi-thread runtime for the sync wrapper; block_on is called
 # concurrently from rayon worker threads (see src/indexes.rs). `sync` backs the
 # mpsc channel that bridges the blocking upload reader into an async byte stream.