[BE-39] Add Workspace Opening Hours Validator with multi-error reporting

[devwums]

Problem

No validation exists for workspace opening hours configuration. Workspaces can be saved with contradictory schedules (e.g., close time before open time, duplicate days) without any error.

Proposed Solution

Create backend/cntr/opening-hours.validator.ts exporting OpeningHoursEntry interface ({ dayOfWeek: 0|1|2|3|4|5|6, openTime: string, closeTime: string, isClosed: boolean }), ValidationResult interface ({ isValid: boolean, errors: string[] }), and validateOpeningHours(hours: OpeningHoursEntry[]): ValidationResult. Checks: valid HH:MM format, closeTime > openTime (unless isClosed), no duplicate dayOfWeek. All implementation must live inside backend/cntr/.

Acceptance Criteria

• File at backend/cntr/opening-hours.validator.ts
• Validates HH:MM format with a regex
• Rejects closeTime <= openTime when isClosed = false
• Rejects duplicate dayOfWeek entries
• Returns ALL errors at once (not fail-fast)
• Unit test at backend/cntr/opening-hours.validator.spec.ts

[Amas-01]

@Amas-01 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hello Maintainer
I'll like to work on this Issue

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[Tyler7x]

@Tyler7x has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hey,

I'd love to take this on.

I’ve spent a good amount of time contributing to projects and working through existing codebases, so I’m comfortable jumping in, understanding the requirements, and implementing changes that fit the project's style and structure.

I’ve reviewed the issue and feel confident about tackling it. Happy to work on it if it’s still available.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Tyler7x to this issue.

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Congratulations, @Tyler7x! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

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This issue has been completed by @Tyler7x as part of the Stellar Wave Program's 5th Wave 🥳

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