feat: add per-load key to load_managed_table

[shefeek-jinnah]

What

Adds an optional key argument to load_managed_table (on both ManagedDatabaseClient and RuntimeClient), forwarded into LoadManagedTableRequest.key. This lets delete/update/upsert loads carry their merge key per-load instead of requiring it to be declared at table creation. Omit key to use the table's declared key; ignored for replace/append (fully backward compatible).

client.load_managed_table("db", "orders", schema="public", upload_id=u, mode="delete", key=["id"])

Depends on

hotdata>=0.8.0 (adds the key field to LoadManagedTableRequest). ✅ Published to PyPI, and uv.lock is locked to it in this PR.

Part of the per-load-key chain

runtimedb (server, merged & deployed) → hotdata 0.8.0 (merged & published) → this PR → hotdata-dlt-destination (connector, next). A follow-up release PR bumps this package 0.7.3 → 0.8.0.

Tests

• test_load_managed_table_forwards_key — the key is forwarded through ManagedDatabaseClient to the runtime client.
• test_load_managed_table_passes_key / test_load_managed_table_key_defaults_to_none — the key flows into LoadManagedTableRequest and defaults to None when omitted.
• Full suite passes (green in CI: Test (Python 3.12), changelog check, review). Verified locally against hotdata 0.8.0.

[claude]

Clean, focused change. key is threaded consistently through both the runtime and managed clients (mirroring mode), tests cover forwarding at both layers plus the default-None case, and CHANGELOG/dependency bump are handled. LGTM.

[claude]

Clean, well-tested passthrough of the per-load key. Threaded correctly through both client layers, defaults to None, retry semantics unchanged, and covered at both levels. LGTM.