feat(beta): add beta testing features and privacy policy page

Implemented comprehensive beta testing system with tier badges and
reorganized environment configuration for better maintainability.

Beta Testing Features:
- Beta banner component with dismissible state (localStorage)
- Auto-assign SUPPORTER tier to new registrations (env controlled)
- TierBadge component with SUPPORTER/COMFORT tier display
- Badge shown in Navbar, ProfilePage, and PublicProfilePage
- Environment variables: VITE_BETA_MODE, BETA_AUTO_SUPPORTER

Environment Configuration Reorganization:
- Moved .env files from root to frontend/ and backend/ directories
- Created .env.{development,production}{,.example} structure
- Updated docker-compose.yml to use env_file for frontend
- All env vars properly namespaced and documented

Privacy Policy Implementation:
- New /privacy route with dedicated PrivacyPage component
- Comprehensive GDPR/RODO compliant privacy policy (privacy.html)
- Updated CookieConsent banner to link to /privacy
- Added Privacy Policy links to all footers (HomePage, PublicFooter)
- Removed privacy section from About Us page

HTML Content System:
- Replaced react-markdown dependency with simple HTML loader
- New HtmlContentPage component for rendering .html files
- Converted about-us.md and how-it-works.md to .html format
- Inline CSS support for full styling control
- Easier content editing without React knowledge

Backend Changes:
- Registration auto-assigns SUPPORTER tier when BETA_AUTO_SUPPORTER=true
- Added accountTier to auth middleware and user routes
- Updated public profile endpoint to include accountTier

Files:
- Added: frontend/.env.{development,production}{,.example}
- Added: backend/.env variables for BETA_AUTO_SUPPORTER
- Added: components/BetaBanner.jsx, TierBadge.jsx, HtmlContentPage.jsx
- Added: pages/PrivacyPage.jsx
- Added: public/content/{about-us,how-it-works,privacy}.html
- Modified: docker-compose.yml (env_file configuration)
- Modified: App.jsx (privacy route, beta banner)
- Modified: auth.js (auto SUPPORTER tier logic)

frontend/src/App.jsx

@@ -26,10 +26,12 @@ import ContactMessagesPage from './pages/admin/ContactMessagesPage';
 import ContactPage from './pages/ContactPage';
 import AboutUsPage from './pages/AboutUsPage';
 import HowItWorksPage from './pages/HowItWorksPage';
+import PrivacyPage from './pages/PrivacyPage';
 import NotFoundPage from './pages/NotFoundPage';
 import VerificationBanner from './components/common/VerificationBanner';
 import InstallPWA from './components/pwa/InstallPWA';
 import CookieConsent from './components/common/CookieConsent';
+import BetaBanner from './components/BetaBanner';
 
 // Protected Route Component with Verification Banner
 const ProtectedRoute = ({ children }) => {
@@ -98,6 +100,9 @@ function App() {
     <BrowserRouter>
       <AuthProvider>
         <AnalyticsWrapper>
+          {/* Beta Testing Banner */}
+          <BetaBanner />
+
           {/* PWA Install Prompt */}
           <InstallPWA />
 
@@ -263,6 +268,9 @@ function App() {
           {/* How It Works Page - Public route */}
           <Route path="/how-it-works" element={<HowItWorksPage />} />
 
+          {/* Privacy Policy Page - Public route */}
+          <Route path="/privacy" element={<PrivacyPage />} />
+
           {/* Public Profile - /u/username format (no auth required) */}
           <Route path="/u/:username" element={<PublicProfilePage />} />