ENG-3842: Add configurable pool_recycle for database connections

[erosselli]

Ticket ENG-3842

Description Of Changes

Adds a new FIDES__DATABASE__POOL_RECYCLE configuration setting (Optional[int], must be > 0) that controls SQLAlchemy's pool_recycle across all engine types (API sync, API async, task, async readonly). When set, connections older than this many seconds are automatically closed and replaced. This is useful when a connection proxy or firewall imposes an idle connection timeout.

When unset (None, the default), connections are never recycled — preserving current behavior with zero impact on existing deployments.

Code Changes

• Added pool_recycle field to DatabaseSettings in database_settings.py
• Added pool_recycle parameter to get_db_engine() in session.py, conditionally passed to create_engine
• Wired pool_recycle through to all engine creation sites: session_management.py, tasks/__init__.py, ctl_session.py
• Added config, session, deps, and task engine tests

Steps to Confirm

1. Set FIDES__DATABASE__POOL_RECYCLE=1800 and verify the setting is picked up on startup
2. Verify setting FIDES__DATABASE__POOL_RECYCLE=0 or a negative value is rejected by config validation
3. Verify existing behavior is unchanged when the setting is not provided

Pre-Merge Checklist

• Issue requirements met
• All CI pipelines succeeded
• CHANGELOG.md updated
  • Add a db-migration This indicates that a change includes a database migration label to the entry if your change includes a DB migration
  • Add a high-risk This issue suggests changes that have a high-probability of breaking existing code label to the entry if your change includes a high-risk change (i.e. potential for performance impact or unexpected regression) that should be flagged
  • Updates unreleased work already in Changelog, no new entry necessary
• UX feedback:
  • No UX review needed
• Followup issues:
  • No followup issues
• Database migrations:
  • No migrations
• Documentation:
  • Documentation issue created in fidesdocs
  • No documentation updates required

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2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
fides-plus-nightly	Ignored	Preview	May 18, 2026 0:32am
fides-privacy-center	Ignored		May 18, 2026 0:32am

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.61%. Comparing base (2c3849a) to head (d450f90).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8209   +/-   ##
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  Coverage   85.61%   85.61%           
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  Files         658      658           
  Lines       42869    42872    +3     
  Branches     5019     5020    +1     
=======================================
+ Hits        36701    36705    +4     
  Misses       5063     5063           
+ Partials     1105     1104    -1     

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[rayharnett]

Very small change to make the pool_recycle setting configurable for SQLAlchemy. No issues identified.