fix(ipc): increase scanner buffer size to 5MB to handle large outputs

[rohitgulia]

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• I have read through the Contributing Documentation.
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Summary

This PR increases the scanner buffer size from the default 64KB to 5MB in the IPC process utility (backend/core/utils/ipc.go). This fixes an issue where large outputs from subprocesses would be truncated when exceeding the 64KB buffer limit.

Changes:

• Updated scanOutputPipe() function to set buffer size to 5MB
• Updated scanErrorPipe() function to set buffer size to 5MB

This allows DevLake to properly handle large outputs from subprocess calls, particularly important for plugins that process large data payloads.

Does this close any open issues?

N/A (Please reference if applicable)

Screenshots

N/A

Other Information

• Type: Bug Fix (pr-type/bug-fix)
• Impact: Fixes subprocess output truncation for large outputs
• Testing: Existing unit tests pass; buffer size increase is backward compatible with existing code

[klesh]

I believe increasing the buffer size is a good idea. Would it be better to expose an Environment Variable to allow users to customize it?