feat(timetable-import): split multi-teacher lessons into one lesson per teacher

[Dasa122]

Summary

A source lesson that carries multiple teachers was imported as one row with a teacherIds array, so a substitution or a moved lesson could not target a single one of those teachers. processLesson now emits one lesson draft per teacher.

Changes

• processLesson returns LessonDraft[]: a lesson resolving to more than one teacher becomes one draft per teacher, keeping the same cohorts, groups, classrooms, subject, day, period, term, week and periodsPerWeek; 0/1-teacher lessons stay a single draft.
• scheduleKey is now <lessonIndex>:<draftIndex>.
• Importer only — no migration, adapters or frontend changes. Each import creates a new timetable, so existing merged rows are superseded on the next import.

Verification

• bun run lint
• bun run typecheck
• bun run build — if bundler config, routers, or server entrypoints changed
• Translations added to both apps/iris/public/locales/en/translation.json and apps/iris/public/locales/hu/translation.json — if user-facing text changed
• Migration generated with bun run db:generate and committed — if the schema changed

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🔇 Additional comments (1)

packages/timetable-import/src/import.ts (1)

1114-1114: LGTM!

Also applies to: 1118-1118, 1129-1129, 1158-1158, 1259-1259

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📝 Walkthrough

Walkthrough

processLesson now returns an array of lesson drafts. It returns no drafts when required mappings are unresolved and creates one draft per distinct mapped teacher when a lesson has multiple teachers. loadLessons appends every returned draft.

Changes

Lesson draft processing

Layer / File(s)	Summary
Process and load lesson drafts packages/timetable-import/src/import.ts	processLesson returns an array, skips unresolved lessons with an empty array, and creates separate drafts for multiple distinct mapped teachers. Each draft receives its own row, key, and schedule key. loadLessons appends all returned drafts.

Priority: ⬇️ Low

Merge Risk: ⚪ Minimal · up to 398c5

The teacher-specific lesson rows appear mergeable after normal checks; no concrete blocking issue was established.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly describes the main change: splitting multi-teacher timetable lessons into one lesson per teacher.
Description check	✅ Passed	The description follows the required Summary, Changes, and Verification sections. It explains the behavior change, scope, and verification results. The issue reference after "Closes #" is blank, but t…
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.

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