feat(client): allow configuring TLS verification

[albert20260301]

Summary

• add a verify parameter to Client(...) and forward it to the underlying httpx.Client
• cover both supported cases requested in the issue: False and an ssl.SSLContext
• document the verify=False development use case in the README
• make the existing Docker test fixture store the mapped port as a string so the suite runs cleanly on Python 3.14

Impact analysis

• affects only Python SDK client initialization in altertable-lakehouse-python
• default behavior is unchanged because verify defaults to True
• unblocks local and custom CA / self-signed TLS setups without changing request semantics for existing users

Tests

• pytest
• ruff check .

Cross-SDK check

• checked altertable-ai/altertable-python: its client already exposes a transport-level option (timeout) but does not currently expose TLS verification controls, so this PR does not introduce an established cross-SDK inconsistency to mirror or unwind

Spec alignment

• this is a client transport configuration surface, not a spec-defined API field, so there is no request/response spec divergence

Closes #7