docs: add full wiki with 74 pages, assets, and CI workflow

Adds the complete TREK documentation wiki covering installation,
trip planning, admin panel, MCP/AI integration, addons, and operations.

Also fixes encrypt-at-rest gaps: mapbox_access_token, Synology
credentials, per-user webhook/ntfy tokens, and photo passphrases
are now rotated by migrate-encryption.ts and stored encrypted via
settingsService.

wiki/Languages.md

@@ -0,0 +1,51 @@
+# Languages
+
+TREK ships with translations for 15 languages. You can change your language at any time without logging out.
+
+## Supported languages
+
+| Code | Language |
+|------|----------|
+| `de` | Deutsch |
+| `en` | English |
+| `es` | Español |
+| `fr` | Français |
+| `hu` | Magyar |
+| `nl` | Nederlands |
+| `br` | Português (Brasil) |
+| `cs` | Česky |
+| `pl` | Polski |
+| `ru` | Русский |
+| `zh` | 简体中文 |
+| `zh-TW` | 繁體中文 |
+| `it` | Italiano |
+| `ar` | العربية |
+| `id` | Bahasa Indonesia |
+
+## RTL support
+
+Arabic (`ar`) uses a right-to-left layout. All other languages use left-to-right.
+
+## How language is detected
+
+TREK resolves the display language in this order:
+
+1. **User preference** — the language saved to your account (set in Settings → Display).
+2. **Browser language** — `navigator.languages` (and `navigator.language`) reported by your browser.
+3. **Server default** — the `DEFAULT_LANGUAGE` environment variable set by the admin.
+4. **Fallback** — English (`en`).
+
+## Where the language picker appears
+
+- **Login / Register page** — before you are signed in.
+- **Settings → Display** — after you are signed in. See [Display-Settings](Display-Settings).
+- **Public share pages** — trip share links.
+- **Public journey pages** — public-facing journey views.
+
+> **Admin:** The `DEFAULT_LANGUAGE` environment variable sets the fallback language shown on the login page and for unauthenticated users. See [Environment-Variables](Environment-Variables).
+
+## See also
+
+- [Display-Settings](Display-Settings)
+- [Environment-Variables](Environment-Variables)
+- [User-Settings](User-Settings)