Enhancement: Network reliability improvements

[dshkol]

Summary

Reliability improvements for StatCan API instability:

M3: Retry helpers drop warn_only on recursive retries

• Files: R/cansim_helpers.R:155, R/cansim_helpers.R:205
• Issue: warn_only parameter not passed on recursive retry calls
• Impact: Warn-only calls can error after retry

M4: Some API calls bypass retry helpers

• Files: R/cansim.R:956, R/cansim.R:1006, R/cansim_metadata.R:203
• Issue: get_cansim_table_url, get_cansim_changed_tables, get_cansim_cube_metadata don't use retry
• Impact: Network failures not handled gracefully

Proposed Fix

• M3: Pass warn_only through recursive calls
• M4: Route all API calls through get_with_timeout_retry

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From code audit - reliability for StatCan API instability