Track deferred major dependency upgrades (React 19, antd 6, redux 5, i18next 26, ESLint 10, TypeScript 7, ...)

[KirDE]

Context

During a dependency-update pass on dependecy-update, everything that could be safely updated within its existing semver range was bumped (types packages, prettier, i18next/react-i18next patch releases, react-markdown, ua-parser-js, less, etc. — see that PR for details). The packages below are pinned behind a major version gap and were deliberately left alone, since each needs dedicated migration/testing rather than a blind bump.

Deferred major upgrades

Package	Current	Latest	Notes
react / react-dom	18.3.1	19.2.8	Root of several other blocked upgrades below
react-leaflet / react-leaflet-cluster	4.2.1 / 2.1.0	5.0.0 / 4.1.3	react-leaflet 5 requires React 19
antd	4.24.16	6.6.1	Two majors behind; large UI-library migration
redux / react-redux / redux-thunk	4.2.1 / 7.2.9 / 2.4.2	5.0.1 / 9.3.0 / 3.1.0	Move together; react-redux 8/9 drops legacy context API used here
i18next / react-i18next	23.16.8 / 15.7.4	26.4.0 / 17.0.12	Move together
eslint / eslint-plugin-react-hooks / eslint-config-prettier	9.39.5 / 5.1.0 / 9.1.2	10.8.1 / 7.1.1 / 10.1.8	ESLint 10 dropped support for older Node; check plugin compat first
typescript	5.9.3	7.0.2	Skips a major (6); full project type-check needed
ua-parser-js	0.7.41	2.0.10	Breaking API rewrite in 1.x/2.x
react-intersection-observer	10.1.0	11.0.0
react-markdown	9.1.0	10.1.0
vite-plugin-svgr	4.5.0	5.2.0
leaflet.locatecontrol / @types/leaflet.locatecontrol	0.81.1 / 0.74.6	0.90.1 / 0.82.1
@types/node	22.20.1	26.2.0	Should track the Node major actually used, not necessarily "latest"

Suggested approach

Tackle in small, independently-testable groups rather than one big bump: e.g. (1) i18next + react-i18next, (2) redux + react-redux + redux-thunk, (3) React 19 + react-leaflet 5 + react-leaflet-cluster, (4) antd, (5) tooling (eslint/typescript/vite-plugin-svgr). Each group should get its own build/lint/test pass and a manual smoke test in the browser before merging.