feat(api): harden compression and index audit queries

[Quanwritescodes]

Summary

Addresses #1531 and #1532.

#1531: Compression policy

• Restricts compression to JSON and text responses.
• Excludes text/event-stream and responses that already carry Content-Encoding.
• Skips known response bodies smaller than 32 bytes.
• Adds module documentation and tests for large/small JSON, SSE, and pre-encoded responses.

#1532: Audit query indexes

• Adds and registers composite indexes for action/time and resource-type/time filters.
• Adds an EXPLAIN-based integration test for actor/time, action/time, resource-type/time, and statistics date-range queries.

The active audit logger uses audit_log and timestamp, rather than the issue’s audit_logs and created_at; the migration and plan test follow the current code and schema.

closes #1531
closes #1532

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