chore: [DHIS2-21506] Consolidate me API requests

[henrikmv]

DHIS2-21506

Introduces a CurrentUser singleton, populated once at app startup from a single /me request, and replaces ~10 runtime /me fetches scattered across hooks and epics with synchronous reads.

init.ts already fetches /me at startup. This PR widens that fetch to include the fields previously queried ad-hoc (firstName, surname, username, userRoles{id}) and stores the result in a new CurrentUser class:

// Before: every consumer re-fetched /me
const { data } = useDataQuery({ me: { resource: 'me', params: { fields: '...' } } });
const locale = data?.me?.settings?.keyUiLocale;

// After: single init-time fetch, synchronous access
const locale = CurrentUser.get().uiLocale;

This change should not increase the initial payload size in practice.

It adds three small scalar fields — firstName, surname, and username — but reduces the amount of data requested for the four list fields: userRoles, userGroups, organisationUnits, and teiSearchOrganisationUnits.

For those collections, the request now fetches only id(and path where needed)

Removed	Replaced by
useUserLocale hook (5 call sites)	CurrentUser.get().uiLocale
useUserRoles hook (WidgetProfile)	CurrentUser.get().userRoles
useNoteDetails hook (WidgetEventSchedule)	CurrentUser.get() + generateUID() inline
useDataQuery({ me }) in OrgUnitField	CurrentUser.get().organisationUnits
useApiMetadataQuery('me') in useSearchScopeWithFallback	CurrentUser.get().{teiSearchOrganisationUnits, organisationUnits}
querySingleResource('me') in 5 note epics	CurrentUser.get()

[github-actions]

🚀 Deployed on https://deploy-preview-4562.capture.netlify.dhis2.org

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 6 additional findings.

[simonadomnisoru]

Great refactor initiative @henrikmv 🙌 ! My only concern is whether the two self-contained widgets should be included or not. I'm curious to hear your thoughts on this. Thanks!

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud