Remove bridge sync indexing cap

[ewlarson]

Summary

• Remove the hard total cap on bridge delta Elasticsearch refreshes so every changed resource ID is handled.
• Process bridge Elasticsearch refresh work in configurable batches of 5,000 by default.
• Process bridge cache invalidation/generated asset refresh work in configurable batches of 5,000 by default while keeping URL rewarm bounded.
• Keep the old BRIDGE_SEARCH_INDEX_MAX_RESOURCE_IDS and BRIDGE_CACHE_REFRESH_MAX_RESOURCE_IDS env vars as compatibility aliases for batch size, not total limits.
• Add bridge sync report warnings for partial Elasticsearch refreshes and cache refresh failures.
• Add tests for uncapped batched indexing/cache invalidation and the new report warnings.

Root Cause

The May 23 production bridge run imported 8,945 changed resources, but the targeted Elasticsearch refresh only processed the first 5,000 IDs. That left a tail of stale ES documents/facets even though the database rows had the corrected provider/publisher values.

Implementation Notes

The fix keeps the operational guardrail that large deltas should be chunked. The 5000 value now controls batch size, so a 300K-item delta is processed as multiple batches rather than one giant request or a truncated first slice.

Validation

• BTAA_SKIP_TEST_DB=true python -m pytest backend/tests/services/test_bridge_search_index.py backend/tests/services/test_bridge_cache_refresh.py backend/tests/services/test_bridge_sync_report.py
• ruff format --check backend/app/services/bridge_sync/search_index.py backend/app/services/bridge_sync/cache_refresh.py backend/app/services/bridge_sync/report.py backend/tests/services/test_bridge_search_index.py backend/tests/services/test_bridge_cache_refresh.py backend/tests/services/test_bridge_sync_report.py
• ruff check backend/app/services/bridge_sync/search_index.py backend/app/services/bridge_sync/cache_refresh.py backend/app/services/bridge_sync/report.py backend/tests/services/test_bridge_search_index.py backend/tests/services/test_bridge_cache_refresh.py backend/tests/services/test_bridge_sync_report.py
• git diff --check

Refs #145