Modernize the embedded web UI: React 19, Vite 8, TypeScript 7

[Sbussiso]

All five open /web bumps as one change, because four of them could not
land separately.

package	from	to	PR
hls.js	1.6.16	1.7.3	#26
react + @types/react	18.3.1	19.3.0	#30
react-dom + @types/react-dom	18.3.1	19.3.0	#29
typescript	5.9.3	7.0.2	#21
@vitejs/plugin-react	4.7.0	6.1.1	#27
vite	5.4.21	8.3.0	no PR

Why #27 was stuck

@vitejs/plugin-react 6 declares a peer of vite: ^8.0.0, and this
project is on vite 5. No Dependabot PR bumped vite, so #27 could never merge
on its own — it needed a three-major vite jump nothing was proposing.
react/react-dom and their @types are likewise two pairs that have to
move together.

One source change, and it's a pre-existing gap

TypeScript 7 rejects the side-effect CSS import in main.tsx:

src/main.tsx(15,8): error TS2882: Cannot find module or type declarations
for side-effect import of './styles.css'.

The project never had src/vite-env.d.ts — the
/// <reference types="vite/client" /> file npm create vite scaffolds,
which declares the module shapes Vite invents at build time (*.css,
import.meta.env, …). TypeScript 5 let the untyped import slide; 7 doesn't.
Added, with a comment recording why.

Verification

This is React 18 → 19 and a rolldown-based Vite, so "it compiles" isn't
enough.

Build: npm run build (tsc -b && vite build) — clean, 0 type errors.

Actually rendered it: served the built bundle with vite preview and
loaded it in headless Chromium. The post-JS DOM carries the real shell:

<div id="root"><div class="app-shell"><header class="app-header">
<div class="app-brand">…<div class="app-brand-text">Sentinel</div>…

…with the Cameras / Snapshots / Recordings / Local nav present, so
react-router works under 19. With no backend behind the preview server the
page shows "Couldn't load cameras — Request failed with status 502" plus
the Command Center upsell card — the correct degraded state, not a blank
page. Chromium's console had no app-level errors and no React warnings
(only Chromium's own GPU/sandbox infrastructure noise).

Bonus

Vite 8 builds with rolldown: 51 packages dropped from the tree, and the
build goes from ~1.7s to ~0.4s.

Closes #21
Closes #26
Closes #27
Closes #29
Closes #30

🤖 Generated with Claude Code