Add stable data-cy selectors for Cypress E2E tests

[kmdvs]

Summary

Begins the migration described in #2284 by adding stable semantic data-cy
hooks to the calendar selector and calendar dropdown.

This PR is intentionally limited to testability hooks and does not change
application behaviour, styling, layout, or business logic.

Changes

• Add stable hook for the calendar selector trigger
• Add stable hook for the currently selected calendar name
• Add stable hook for the calendar search input
• Add stable hooks for the calendar list and calendar items
• Add hooks for calendar loading and empty states
• Add the same calendar selector hooks to the responsive sidebar

These hooks replace Cypress selectors coupled to Ant Design DOM structure,
CSS classes, and positional selectors.

Refs #2284

[kmdvs]

Selector stability / #2284 progress

Baseline

Metric	Baseline
Cypress selector definitions	~722
Selectors containing data-cy	~437
data-cy coverage	~60.5%
Selectors with no data-cy	~285 / ~39.5%
Estimated Footlight work packages	~20
Estimated semantic hook additions	~45–60

data-cy coverage is an optimistic proxy for stability. Some selectors still combine data-cy with Ant Design classes, generated DOM structure, or positional selectors.

Progress

Area	Status	Notes
Calendar selector/dropdown	✅ Done	Stable calendar, item, search, list and selected-name hooks
Event list rows	✅ Done	Semantic repeated event-row hook
Event action menu	✅ Done	Stable action trigger
Confirmation modals	✅ Done	Shared title/content/OK/cancel contract
Generic entity deletion	✅ Done	Uses semantic entity rows/actions
Pagination	🚧 In progress	Replace AntD pagination DOM selectors
Searchable filters	⬜ Remaining	AntD checkbox/dropdown internals
Navigation	⬜ Remaining	Replace menu/path/AntD ancestry selectors
Login/profile	⬜ Remaining	Several IDs/CSS/AntD selectors remain
Date controls	⬜ Remaining	AntD picker internals
Time controls	⬜ Remaining	Heavy positional/AntD DOM coupling
TreeSelect / Select	⬜ Remaining	Roots often exist; option/dropdown hooks still needed
Rich-text editors	⬜ Remaining	Quill DOM coupling
Settings / Widget	⬜ Remaining	Mix of stable hooks and structural selectors

Remaining Footlight-side work

Regression importance	Lower effort	Medium / higher effort
High	Navigation, edit/action buttons, pagination, sort controls, login/profile basics, remaining entity-list actions	Searchable filters, bilingual tabs, date picker, time picker, TreeSelect/Select, rich-text editors
Lower	Static Settings/Widget/User Management hooks	Complex Settings/User Management dropdowns and Widget select/tree controls

Example

Before	After
.ant-pagination-next > .ant-pagination-item-link > .anticon > svg	[data-cy="pagination-next"]
div.ant-spin-container ul.ant-list-items :nth-child(1) [data-cy="span-event-name"]	[data-cy="list-item-event"] + Cypress .eq(0)
.outlined-label	semantic action-specific data-cy

Refs #2284

[kmdvs]

#2284 progress

Area	Status	Notes
Calendar selector / dropdown	✅ Done	Stable hooks for selector, selected name, search, list, items, loading and empty state
Event list rows	✅ Done	Semantic repeated list-item-event hook
Event action trigger	✅ Done	Stable event action-menu trigger
Event action menu	✅ Done	Semantic event-action-menu-item hooks with data-action
Event edit button	✅ Done	Dedicated button-edit-event hook
Confirmation modals	✅ Done	Shared title/content and confirm/cancel hooks
Generic entity deletion	✅ Done	Cypress now targets semantic entity rows and delete controls
Pagination	✅ Done	Shared paginationItemRender, page hooks, data-page, next-page hook
Searchable filters	✅ Done	Stable options, option and checkbox hooks; organizer-filter hook corrected
Sidebar navigation	✅ Done	Shared navigation-item hook with data-path and data-active
User profile menu	✅ Done	Stable trigger, username and semantic menu-action hooks
Login / reset-password controls	⬜ Remaining	Several selectors still depend on IDs, AntD classes or DOM structure
Sort dropdowns / menu options	⬜ Remaining	Still includes generated data-menu-id and AntD dropdown selectors
Date picker	⬜ Remaining	AntD-controlled date-input/calendar selectors remain
Time picker	⬜ Remaining	AntD-controlled time-picker selectors remain
TreeSelect / Select	⬜ Remaining	Several selectors still combine data-cy with AntD internals
Rich-text editors	⬜ Remaining	Quill / editor implementation selectors remain
Bilingual tabs	⬜ Remaining	Some tab interactions still depend on AntD structure
Entity-list bespoke actions	⬜ Remaining	Remaining Places / Organizations / People / Taxonomy-specific brittle actions
Settings static UI	⬜ Remaining	Additional brittle Settings selectors remain
User Management static listing	⬜ Remaining	Some listing selectors still need semantic hooks
User Management menus / actions	⬜ Remaining	Generated rc-menu-*, data-menu-id and AntD dropdown selectors remain
Widget static UI	⬜ Remaining	Additional selector cleanup remains
Widget complex selects / trees	⬜ Remaining	AntD Select / TreeSelect structure still used

[kmdvs]

@codex