feat(frontend): add PL/EN i18n using @inlang/paraglide-js v2

- Install @inlang/paraglide-js v2 with Vite plugin and paraglideMiddleware hook
- Add messages/pl.json and messages/en.json with ~400 translation keys
- Create project.inlang/settings.json (PL as base locale)
- Add LanguageSwitcher component (cookie-based, no URL prefix needed)
- Replace all hardcoded strings across 14 pages/components with m.*() calls
- ProductForm uses derived label maps for all enum types (category, texture, etc.)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/project.inlang/settings.json

@@ -0,0 +1,12 @@
+{
+	"$schema": "https://inlang.com/schema/project-settings",
+	"baseLocale": "pl",
+	"locales": ["pl", "en"],
+	"modules": [
+		"https://cdn.jsdelivr.net/npm/@inlang/plugin-message-format@4/dist/index.js",
+		"https://cdn.jsdelivr.net/npm/@inlang/plugin-m-function-matcher@2/dist/index.js"
+	],
+	"plugin.inlang.messageFormat": {
+		"pathPattern": "./messages/{locale}.json"
+	}
+}