backport: refactor(database): wrap connection in Arc<Mutex> and add shared_connection()

[lklimek]

Summary

• Changes Database.conn from Mutex<Connection> to Arc<Mutex<Connection>>
• Adds shared_connection() method to get a cloneable reference to the underlying connection
• All existing code continues to work identically (same lock semantics)
• Enables future consumers to share the SQLite connection without going through Database methods

Test plan

• Build succeeds with no warnings
• All existing tests pass
• Database operations work identically (no behavioral change)

_{🤖 Co-authored by Claudius the Magnificent AI Agent}

Summary by CodeRabbit

• Chores
  • Enhanced database connection management to support concurrent access scenarios

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

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Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 9b42950 and b8bf56d.

📒 Files selected for processing (1)

• src/database/mod.rs

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📝 Walkthrough

Walkthrough

The database connection storage is refactored from Mutex<Connection> to Arc<Mutex<Connection>> to enable shared thread-safe access across components. Imports are updated to include Arc, and a new public method shared_connection() is added to return clones of the wrapped connection for sharing.

Changes

Cohort / File(s)	Summary
Database Connection Refactoring src/database/mod.rs	Swapped connection storage mechanism from Mutex<Connection> to Arc<Mutex<Connection>>. Updated imports to include Arc. Added new public method shared_connection() that returns a clone of the Arc<Mutex<Connection>> for callers to share the underlying connection. Execute path remains functionally unchanged.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 A burrow of threads, now safely aligned,
With Arc's gentle touch, no locks left behind,
Connections are shared where the rabbits all meet,
Mutex and Arc make the synchronization sweet! 🔄✨

✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch zk-extract/db-arc-mutex

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