Upgrade rack to 3.2.4 by updating oauth2 and removing jeweler

[Copilot]

Rack was locked at 2.2.4 due to transitive dependency constraints. Upgraded to 3.2.4 (latest).

Changes

• Dependencies: Upgraded oauth2 1.4.8 → 2.0.18 (enables rack 3.x via relaxed constraint < 4 instead of < 3)
• Gemfile: Added explicit constraints oauth2 >= 2.0 and rack >= 3.0 to override transitive dependencies
• Removed jeweler: Incompatible with oauth2 2.x; gem management tasks unavailable but optional (Rakefile already handles absence)
• Configuration: Added vendor/bundle and .bundle to .gitignore

Result

# Before
rack (2.2.4)
oauth2 (1.4.8)
  rack (>= 1.2, < 3)

# After  
rack (3.2.4)
oauth2 (2.0.18)
  rack (>= 1.2, < 4)

All tests pass (26 tests, 67 assertions). No security vulnerabilities detected.

Original prompt

Upgrade rack to the highest possible version. Some dependencies lock it down to 2.2.4, so upgrade everything as needed to get it to the most recent version possible. Fix any issues that arise.

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