feat(dataviewer): plan incremental frontend framework migration (React 19, Tailwind 4, TS 6, Vite 8)

[katriendg]

Context

Dependabot PR #460 attempted to bump 29 frontend packages simultaneously, including 6+ major version upgrades. The PR fails CI because these are breaking changes requiring code migration. PR #460 will be closed.

Scope

Migrate the dataviewer frontend through these major framework upgrades incrementally, one at a time, with passing CI at each step:

Package	Current	Target	Migration Complexity
Tailwind CSS	3.4	4.x	High — CSS-first config, @import syntax, no tailwind.config.js
React	18.3	19.x	High — forwardRef removal, ref as prop, hooks behavior
TypeScript	5.6	6.x	Medium — stricter type checking
Vite	6.4	8.x	Medium — plugin API changes
ESLint	9.x	10.x	Low — flat config updates
MSAL browser/react	4.x/3.x	5.x/5.x	Medium — new auth API surface
tailwind-merge	2.x	3.x	Low — API alignment with Tailwind 4

Suggested Order

1. Tailwind CSS 3→4 + tailwind-merge 2→3 (foundation — affects all component styling)
2. React 18→19 + @types/react 18→19 (core runtime)
3. TypeScript 5→6 (type system — fix any new errors from steps 1-2)
4. Vite 6→8 + @vitejs/plugin-react (build tooling)
5. ESLint 9→10 + eslint-plugin-react-hooks 5→7 (linting)
6. MSAL 4→5 / 3→5 (auth — test in deployed environment)
7. Minor/patch bumps for remaining packages (lucide-react, recharts, zustand, etc.)

Acceptance Criteria

• Each upgrade is a separate PR with passing CI
• No functionality regressions in the dataviewer UI
• Dependabot .github/dependabot.yml updated to ignore major versions already tracked here
• All shadcn/ui components validated after Tailwind 4 migration