fix (full-sync): Adding pino logger for probot update

[dolan-a]

With the Probot v14 update, it seems that logging in full-sync no longer works:

$ node --env-file=.env full-sync.js                               
Fatal error during full sync: TypeError: Cannot read properties of null (reading 'info')
    at performFullSync (/home/dol/dev/personal/safe-settings/full-sync.js:7:14)
    at Object.<anonymous> (/home/dol/dev/personal/safe-settings/full-sync.js:25:1)
    at Module._compile (node:internal/modules/cjs/loader:1761:14)
    at Object..js (node:internal/modules/cjs/loader:1893:10)
    at Module.load (node:internal/modules/cjs/loader:1481:32)
    at Module._load (node:internal/modules/cjs/loader:1300:12)
    at TracingChannel.traceSync (node:diagnostics_channel:328:14)
    at wrapModuleLoad (node:internal/modules/cjs/loader:245:24)
    at Module.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:154:5)
    at node:internal/main/run_main_module:33:47

This PR has the following changes:

1. Adds a logger (via already-installed pino)
2. Adds a few unit tests to confirm performFullSync in full-sync runs okay (test fails without the logger change; passes with it)

[dolan-a]

@decyjphr - can we get this considered for an upcoming release?

[Copilot]

Pull request overview

This PR updates the full-sync CLI entrypoint to restore logging compatibility after the Probot v14 upgrade by explicitly providing a logger to createProbot, and adds unit tests around performFullSync to prevent regressions.

Changes:

• Create a pino logger and pass it to createProbot via overrides.log to avoid probot.log being null.
• Add a null-guard around settings.errors to avoid crashing when syncInstallation() returns null.
• Export performFullSync and add unit tests for logger wiring and null-safety.

Show a summary per file

File	Description
full-sync.js	Adds a pino logger override for Probot v14 and exports performFullSync for testing.
test/unit/full-sync.test.js	Introduces unit tests for performFullSync (logger override + null settings).

Copilot's findings

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• Files reviewed: 2/2 changed files
• Comments generated: 3

[decyjphr]

@dolan-a Thanks for the changes. I used Copilot Code review and it suggested a few changes. Could you review and add them?

[marcusburghardt]

It seems also related to #955

[dolan-a]

@decyjphr - Thanks, this is ready for another review