Schedule: Add unit tests to services/supabase/llm_requests/clear_old_content.py

[gitauto-ai]

Resolves #1992

Summary

Add comprehensive unit tests for services/supabase/llm_requests/clear_old_content.py to validate deletion of stale LLM request content across success, edge, and error paths.

Test Patterns

• Deletes rows strictly older than cutoff; preserves newer or boundary (equal to cutoff) rows
• No-op when dataset is empty or no rows meet criteria
• All-eligible scenario: deletes all when everything is older than cutoff
• Cutoff sourcing:
  • Explicit cutoff datetime argument
  • Retention days from environment/config
  • Missing/invalid retention config falls back to default or raises as expected
• Timezone handling and boundary conditions (naive vs aware timestamps; off-by-one second)
• Batched/paginated deletion behavior (if implemented) processes all pages
• Supabase client failures (select/delete errors) are surfaced/handled appropriately
• Idempotency: repeated runs after deletion do not remove additional rows
• Returns expected status/count and emits expected logs/metrics

git fetch origin
git checkout gitauto/issue-1992-20251201-000024-g9kg
git pull origin gitauto/issue-1992-20251201-000024-g9kg