Cache git repo info in session to avoid repeated queries

[everpcpc]

Summary

This PR implements caching of git repository information in the session database to reduce repeated git command executions.

What changed:

• Added 4 cache fields to session types: currentBranch, ownerRepo, isFork, originOwnerRepo
• Created database migration to add these fields to the sessions table
• Implemented fetchAndCacheRepoInfo() function to fetch and cache repo info on first access
• Updated 3 IPC handlers to use cached data:
  • sessions:get-git-commands
  • sessions:get-remote-pull-request
  • sessions:get-pr-remote-commits

Why:
Previously, every call to these handlers would execute git commands to get branch and remote information. This PR caches this data in the session database after the first query, significantly reducing git command overhead.

Testing:

• Added new test file gitCacheHandlers.test.ts with 4 tests covering cache hit/miss scenarios
• Updated existing tests in gitHandlers.test.ts to work with the caching mechanism
• All 50 tests pass (46 existing + 4 new)

Tests

• Unit Test
• Logic Test
• Benchmark Test
• No Test - Explain why

Type of change

• Bug Fix (non-breaking change which fixes an issue)
• New Feature (non-breaking change which adds functionality)
• Breaking Change (fix or feature that could cause existing functionality not to work as expected)
• Documentation Update
• Refactoring
• Performance Improvement
• Other (please describe):