Test/365 js data models unit tests

[suraj-yadav0]

Closes #365

Adds automated QML test coverage for JavaScript data models:

• models/task.js: Assignee parsing, due status calculations, stage classification, priority setting, and local ID mapping.
• models/timesheet.js: Timesheet creation, duration parsing, readiness checks, status transitions, and deleted flags.
• models/project.js: Offline cache operations, project details, favorites toggle, and project updates.
• models/activity.js: Activity ID sanitization, icon mappings, date filtering, and CRUD operations.
• models/accounts.js: Default account handling, duplicate checks, sync settings, and cascade deletion.
• models/notifications.js: Notification payloads, read counts, and sync notification filters.
• models/Main.js: Date calculations, entity name resolution, quadrant differences, and spent hours queries.

All 437 QML unit tests and 54 Python unit tests pass.