fix: reduce GitHub API calls and add configurable timeout

[andrasbacsai]

STRAWBERRY

Changes

• Pre-generate GitHub installation token once per deployment instead of multiple times, reducing API calls from 4-6 down to 2
• Add configurable timeout via GITHUB_API_TIMEOUT env variable (default 30s)
• Add retry logic (3 retries with 200ms delay) for resilience on slow networks
• Pass token through deployment context to avoid regeneration

Issue

• Resolves [Bug]: Build timeout for api.github.com #7769

Category

• Bug fix

AI Usage

• AI is used in the process of creating this PR

Steps to Test

• Step 1 – Set up a private GitHub App source in Coolify
• Step 2 – Deploy an application from that private GitHub repository
• Step 3 – Verify deployment succeeds without timeout errors
• Step 4 – (Optional) Set GITHUB_API_TIMEOUT=60 env var to test custom timeout for very slow networks

Contributor Agreement

Important

• I have read and understood the contributor guidelines. If I have failed to follow any guideline, I understand that this PR may be closed without review.
• I have tested the changes thoroughly and am confident that they will work as expected without issues when the maintainer tests them