refactor: move Slack types to their own file

[santiagofn]

This is the first in a series of PRs that together implement threaded message support for the Slack notifier. The full picture is available in #5150.

Summary

Extracts the Slack notifier's internal types (Notifier, request, attachment, slackResponse) from slack.go into a dedicated types.go file. No behavioral changes.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds configuration files to ignore JetBrains IDE and Slack plans directories, and refactors Slack notifier type definitions into a dedicated types file while preserving existing functionality.

Changes

Gitignore Configuration

Layer / File(s)	Summary
IDE & Plan Exclusions .cursor/.gitignore, .gitignore	Added ignore patterns for .cursor/plans/ and .idea/ directories to exclude Slack plan storage and JetBrains IDE project files.

Slack Notifier Type Refactoring

Layer / File(s)	Summary
Type Definitions notify/slack/types.go	New file introduces exported Notifier struct with configuration, template, logger, HTTP client, and retry fields; adds internal types for Slack API payloads (request, attachment) and responses (slackResponse).
Implementation Cleanup notify/slack/slack.go	Code reorganization with no observable functional changes; type definitions extracted or moved out, existing Notifier initialization and Notify logic remain intact.

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🎯 2 (Simple) | ⏱️ ~8 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main refactoring: extracting Slack types into a separate file, which is the primary change across the diff.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The pull request description provides a clear, concise explanation of the changes, references the related issue, and explains the context within a larger refactoring effort.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[SoloJacobs]

Looks pretty good, just some small nits.

[TheMeier]

Please use the header without date (example config/config.go)

[TheMeier]

There is no specific tools in .gitignore at the moment, I think this is intentional. So I would says this should be remove (same for the new .cursor/.gitignore)