chore(deps): migrate to Svelte 5, Vite 8, and related ecosystem packages

Svelte 5's compatibility mode preserves full Svelte 4 component syntax,
so no .svelte file rewrites are needed. This resolves the peer-dependency
conflicts that blocked Dependabot PRs #475, #480, and #482.

frontend:
- svelte 4.2.12 → 5.55.2
- vite 5.2.6 → 8.0.8
- @sveltejs/vite-plugin-svelte 3.0.2 → 7.0.0
- svelte-chartjs 3.1.5 → 4.0.1
- vite-plugin-static-copy 1.0.2 → 4.0.1
- svelte-check 3.6.8 → 4.4.6
- eslint-plugin-svelte 2.35.1 → 2.46.1
- @types/node 20.11.30 → 22.15.3
- Drop svelte-preprocess in favor of vitePreprocess
- Pin @dfinity/candid@1.0.1 via overrides to preserve compat with @dfinity/agent@1.0.1

cli-releases/frontend:
- svelte 4.2.12 → 5.55.2
- vite 5.4.21 → 8.0.8
- @sveltejs/vite-plugin-svelte 3.0.2 → 7.0.0
- @sveltejs/kit 2.55.0 → 2.57.1
- svelte-check 3.6.8 → 4.4.6
- eslint-plugin-svelte 2.35.1 → 2.46.1

root:
- eslint-plugin-svelte 2.35.1 → 2.46.1

Made-with: Cursor

Author: Kamirus