chore: update dependencies including major upgrades

docs/dependency-upgrade-plan.md

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+# Dependency Upgrade Plan
+
+This document tracks the step-by-step plan for upgrading the Torrust website dependencies,
+starting with the compatible patch/minor updates already applied and then tackling each
+remaining major-version bump in a dedicated branch and PR.
+
+## Status Overview
+
+| Package                                  | Current | Target       | Status  | Branch                              |
+| ---------------------------------------- | ------- | ------------ | ------- | ----------------------------------- |
+| Patch / minor updates (all except below) | various | latest minor | ✅ Done | `chore/update-dependencies-2026-04` |
+| `vite`                                   | 8.x     | 8.x          | ✅ Done | `chore/upgrade-vite-8`              |
+| `@sveltejs/vite-plugin-svelte`           | 7.x     | 7.x          | ✅ Done | `chore/upgrade-vite-8`              |
+| `svelte-sitemap`                         | 3.x     | 3.x          | ✅ Done | `chore/upgrade-svelte-sitemap-3`    |
+| `typescript`                             | 6.x     | 6.x          | ✅ Done | `chore/upgrade-typescript-6`        |
+| `@types/node`                            | 25.x    | 25.x         | ✅ Done | `chore/upgrade-typescript-6`        |
+
+---
+
+## Phase 0 — Patch & minor updates ✅
+
+**Branch:** `chore/update-dependencies-2026-04`  
+**PR:** open against `develop`
+
+All non-breaking updates applied. All checks pass (`format`, `lint`, `check`, `build`).
+
+---
+
+## Phase 1 — vite 7 → 8 + @sveltejs/vite-plugin-svelte 6 → 7 ✅
+
+These two must be bumped together: `@sveltejs/vite-plugin-svelte` v7 requires `vite ^8`.
+
+**Branch:** `chore/upgrade-vite-8`
+
+**Result:** completed successfully. `npm run lint`, `npm run check`, and `npm run build` pass.
+
+**Steps:**
+
+1. Create branch `chore/upgrade-vite-8`
+2. Bump versions:
+   ```bash
+   npm install -D vite@^8 @sveltejs/vite-plugin-svelte@^7
+   ```
+3. Check `vite.config.ts` for any removed/renamed Vite 8 APIs  
+   (see [Vite 8 migration guide](https://vite.dev/guide/migration))
+4. Check `svelte.config.js` for vite-plugin-svelte v7 breaking changes  
+   (see [@sveltejs/vite-plugin-svelte changelog](https://github.com/sveltejs/vite-plugin-svelte/blob/main/packages/vite-plugin-svelte/CHANGELOG.md))
+5. Run `npm run check && npm run lint && npm run build`
+6. Fix any issues
+7. Commit and open PR
+
+**Known risks / things to verify:**
+
+- Vite 8 dropped `server.force` option — check `vite.config.ts`
+- `vite-plugin-imagemin` peer compatibility with Vite 8 (may need upgrade or workaround)
+- HMR and SSR behaviour changes in Vite 8
+
+---
+
+## Phase 2 — svelte-sitemap 2 → 3 ✅
+
+This was a smaller, isolated change.
+
+**Branch:** `chore/upgrade-svelte-sitemap-3`
+
+**Result:** completed successfully. `npm run lint`, `npm run check`, and `npm run build` pass, and `build/sitemap.xml` is generated.
+
+**Steps:**
+
+1. Create branch `chore/upgrade-svelte-sitemap-3`
+2. Bump version:
+   ```bash
+   npm install -D svelte-sitemap@^3
+   ```
+3. Read the [svelte-sitemap v3 changelog](https://github.com/bartholomej/svelte-sitemap/blob/master/CHANGELOG.md) for breaking changes
+4. Update `package.json` `postbuild` script or any sitemap configuration if the CLI interface changed
+5. Run `npm run build` and verify `build/sitemap.xml` is generated correctly
+6. Commit and open PR
+
+**Known risks / things to verify:**
+
+- CLI argument changes in v3
+- Output format differences in the generated sitemap
+- v3 suggests moving from CLI options to a config file (not required for current setup)
+
+---
+
+## Phase 3 — TypeScript 5 → 6 ✅
+
+TypeScript 6 is a significant release with stricter type checking.
+
+**Branch:** `chore/upgrade-typescript-6`
+
+**Result:** completed successfully. `npm run lint`, `npm run check`, and `npm run build` pass with no additional code changes required.
+
+**Steps:**
+
+1. Create branch `chore/upgrade-typescript-6`
+2. Bump version:
+   ```bash
+   npm install -D typescript@^6 @types/node@^25
+   ```
+3. Read the [TypeScript 6 breaking changes](https://devblogs.microsoft.com/typescript/)
+4. Run `npm run check` and fix all new type errors
+5. Update `tsconfig.json` if needed (new `target`/`lib` defaults, removed options)
+6. Run full suite: `npm run check && npm run lint && npm run build`
+7. Commit and open PR
+
+**Known risks / things to verify:**
+
+- Stricter type narrowing may reveal latent type errors
+- `verbatimModuleSyntax` may become default — check `tsconfig.json`
+- `@typescript-eslint` packages may need re-aligning with TS 6 types
+- `@types/node` v25 may introduce typing changes for used Node APIs
+
+---
+
+## General checklist for each phase
+
+Before opening each PR, run the full quality suite:
+
+```bash
+npm run format
+npm run lint
+npm run check
+npm run build
+npm run preview   # manual visual verification
+```
+
+Check for `npm audit` issues introduced by the new versions.