feat: Implement AI response feedback UI and complete high-priority features

Frontend Features:
- Add MessageFeedback component with thumbs up/down buttons
- Positive feedback submits immediately with success toast
- Negative feedback opens dialog for optional text input
- Integrate feedback buttons on all AI assistant messages
- Add success Snackbar confirmation message
- Translation keys added to ai.json (feedback section)

Backend Features:
- Add POST /api/v1/ai/feedback endpoint
- Create FeedbackDto with conversation ID validation
- Implement submitFeedback service method
- Store feedback in conversation metadata with timestamps
- Add audit logging for feedback submissions
- Fix conversationId regex validation to support nanoid format

Legal & Compliance:
- Implement complete EULA acceptance flow with modal
- Create reusable legal content components (Terms, Privacy, EULA)
- Add LegalDocumentViewer for nested modal viewing
- Cookie Consent Banner with GDPR compliance
- Legal pages with AppShell navigation
- EULA acceptance tracking in user entity

Branding Updates:
- Rebrand from "Maternal App" to "ParentFlow"
- Update all icons (72px to 512px) from high-res source
- PWA manifest updated with ParentFlow branding
- Contact email: hello@parentflow.com
- Address: Serbota 3, Bucharest, Romania

Bug Fixes:
- Fix chat endpoint validation (support nanoid conversation IDs)
- Fix EULA acceptance API call (use apiClient vs hardcoded localhost)
- Fix icon loading errors with proper PNG generation

Documentation:
- Mark 11 high-priority features as complete in REMAINING_FEATURES.md
- Update feature statistics: 73/139 complete (53%)
- All high-priority features now complete! 🎉

Files Changed:
Frontend: 21 files (components, pages, locales, icons)
Backend: 6 files (controller, service, DTOs, migrations)
Docs: 1 file (REMAINING_FEATURES.md)

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

maternal-web/components/layouts/AppShell/AppShell.tsx

@@ -19,7 +19,7 @@ import { TabBar } from '../TabBar/TabBar';
 import { useMediaQuery } from '@/hooks/useMediaQuery';
 import { ReactNode } from 'react';
 import { useWebSocket } from '@/hooks/useWebSocket';
-import { Wifi, WifiOff, People, AccountCircle, Settings, ChildCare, Group, Logout } from '@mui/icons-material';
+import { Wifi, WifiOff, People, AccountCircle, Settings, ChildCare, Group, Logout, Gavel } from '@mui/icons-material';
 import { useTranslation } from '@/hooks/useTranslation';
 import { useRouter } from 'next/navigation';
 import { useAuth } from '@/lib/auth/AuthContext';
@@ -192,6 +192,13 @@ export const AppShell = ({ children }: AppShellProps) => {
             <ListItemText>{t('navigation.family')}</ListItemText>
           </MenuItem>
           <Divider />
+          <MenuItem onClick={() => handleNavigate('/legal/privacy')}>
+            <ListItemIcon>
+              <Gavel fontSize="small" />
+            </ListItemIcon>
+            <ListItemText>Legal & Privacy</ListItemText>
+          </MenuItem>
+          <Divider />
           <MenuItem onClick={handleLogout}>
             <ListItemIcon>
               <Logout fontSize="small" color="error" />