fix: improve maintenance date-range sync and validation

[prakash-218]

Summary

In this pull request, the following changes are made:

• updated the backend to reject if the end date is before the start date
• in the frontend, made changes to

• update the endtime, when start datetime is changed and a duration is picked
  

• on updating the end date, the duration gets updated as well.
  

• add utility functions to parse and format date-time

• Resolves On the maintenance creation form, link start and end times together #7044

Please follow this checklist to avoid unnecessary back and forth (click to expand)

• ⚠️ If there are Breaking change (a fix or feature that alters existing functionality in a way that could cause issues) I have called them out
• 🧠 I have disclosed any use of LLMs/AI in this contribution and reviewed all generated content.
  I understand that I am responsible for and able to explain every line of code I submit.
• 🔍 Any UI changes adhere to visual style of this project.
• 🛠️ I have self-reviewed and self-tested my code to ensure it works as expected.
• 📝 I have commented my code, especially in hard-to-understand areas (e.g., using JSDoc for methods).
• 🤖 I added or updated automated tests where appropriate.
• 📄 Documentation updates are included (if applicable).
• 🧰 Dependency updates are listed and explained.
• ⚠️ CI passes and is green.

Screenshots for Visual Changes

• UI Modifications: Highlight any changes made to the user interface.
• Before & After: Include screenshots or comparisons (if applicable).

Event	Before	After
creating/editing maintenance

[github-actions]

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[Copilot]

Pull request overview

This PR improves maintenance scheduling validation and UX by keeping the “single” maintenance start/end datetime fields in sync (unless the user manually overrides the end time) and by rejecting invalid date ranges on both frontend submit and backend model validation.

Changes:

• Add backend validation to reject maintenances where end_date is before start_date.
• Update the maintenance edit/create UI to better sync end time when start time changes (and track “manual end edit” vs programmatic updates).
• Add backend tests covering valid/invalid single-maintenance date ranges.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
server/model/maintenance.js	Adds server-side date-range ordering validation in jsonToBean.
src/pages/EditMaintenance.vue	Adds date parsing/formatting helpers, start/end sync watchers, and client-side submit validation for invalid ranges.
test/backend-test/test-maintenance.js	Adds unit tests for Maintenance.jsonToBean() date-range validation behavior.

Comments suppressed due to low confidence (2)

src/pages/EditMaintenance.vue:935

• This toast error message is hard-coded and bypasses the app’s i18n pattern used elsewhere in this file (e.g., other toastError(this.$t(...)) calls). Please switch this to a $t(...) translation key and add the key to src/lang/en.json so the validation error is localizable.

            if (this.hasInvalidDateRange) {
                this.$root.toastError("End date must be after start date");
                this.processing = false;
                return;

src/pages/EditMaintenance.vue:687

• endDateManuallyEdited is only set when both oldEnd and newEnd are truthy. If the user clears the end datetime and then sets a new one, this watcher will never mark the end date as manually edited (clear makes newEnd falsy, then the next change makes oldEnd falsy). That can cause subsequent start-date edits to unexpectedly keep auto-updating the end date. Consider treating any user-driven change (when not isUpdatingEndDateProgrammatically) as manual, while still ignoring the initial value population during init()/data load.

        singleEndDate(newEnd, oldEnd) {
            if (this.maintenance.strategy !== "single") {
                return;
            }

            if (!oldEnd || !newEnd || this.isUpdatingEndDateProgrammatically) {
                return;
            }

            this.endDateManuallyEdited = true;
        },