Add steam API

[CaoKha]

Summary

• Add stream/v1 WebSocket client (auth, public, subscription, models).
• Restructure package: lnmarkets_sdk.rest_v3 → lnmarkets_sdk.rest.v3.
• Drop account.withdraw_internal / get_internal_deposits / get_internal_withdrawals (endpoints gone from api-rest-v3) and associated models.
• Add account.read_notifications() → PUT /account/notifications.
• Rename examples/basic.py → examples/rest_v3.py; add examples/stream_v1.py.
• Fix update_takeprofit example: open real isolated market trade instead of hardcoded UUID (was returning 400 You do not own this trade).

Changes

Added

• stream/v1 package: client, auth, public, subscription, models (announcements, auth, common, cross, futures, isolated, lifecycle, ohlc, subscription, wallet).
• AccountClient.read_notifications().
• examples/stream_v1.py.

Changed

• Package path rest_v3 → rest/v3.
• Example basic.py → rest_v3.py; take-profit flow opens real trade.
• uv.lock, pyproject.toml updated for new deps.

Removed

• AccountClient.withdraw_internal, get_internal_deposits, get_internal_withdrawals.
• Models: WithdrawInternalParams, WithdrawInternalResponse, InternalDe GetInternalDepositsParams, GetInternalWithdrawalsParams`.

Test plan

• uv run examples/rest_v3.py runs clean.
• uv run examples/stream_v1.py connects, authenticates, receives messages.
• Integration tests pass: `uv run pytest src/lnmarkets_sdk/rest/v3/test
• Imports updated downstream: no lnmarkets_sdk.rest_v3 references rem
• CHANGELOG 0.1.0 accurate.

The merge-base changed after approval.