docs: Add comprehensive multi-child implementation plan

Added detailed implementation plan covering:
- Frontend: Dynamic UI, child selector, bulk activity logging, comparison analytics
- Backend: Bulk operations, multi-child queries, family statistics
- AI/Voice: Child name detection, context building, clarification flows
- Database: Schema enhancements, user preferences, bulk operation tracking
- State management, API enhancements, real-time sync updates
- Testing strategy: Unit, integration, and E2E tests
- Migration plan with feature flags for phased rollout
- Performance optimizations: Caching, indexes, code splitting

Also includes:
- Security fixes for multi-family data leakage in analytics pages
- ParentFlow branding updates
- Activity tracking navigation improvements
- Backend DTO and error handling fixes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

maternal-app/maternal-app-backend/src/modules/children/children.controller.ts

@@ -10,6 +10,7 @@ import {
   HttpCode,
   HttpStatus,
   Query,
+  BadRequestException,
 } from '@nestjs/common';
 import { ChildrenService } from './children.service';
 import { CreateChildDto } from './dto/create-child.dto';
@@ -30,13 +31,7 @@ export class ChildrenController {
     @Body() createChildDto: CreateChildDto,
   ) {
     if (!familyId) {
-      return {
-        success: false,
-        error: {
-          code: 'VALIDATION_ERROR',
-          message: 'familyId query parameter is required',
-        },
-      };
+      throw new BadRequestException('familyId query parameter is required');
     }
 
     const child = await this.childrenService.create(
@@ -55,6 +50,7 @@ export class ChildrenController {
           birthDate: child.birthDate,
           gender: child.gender,
           photoUrl: child.photoUrl,
+          photoAlt: child.photoAlt,
           medicalInfo: child.medicalInfo,
           createdAt: child.createdAt,
         },
@@ -85,6 +81,7 @@ export class ChildrenController {
           birthDate: child.birthDate,
           gender: child.gender,
           photoUrl: child.photoUrl,
+          photoAlt: child.photoAlt,
           medicalInfo: child.medicalInfo,
           createdAt: child.createdAt,
         })),
@@ -107,6 +104,7 @@ export class ChildrenController {
           birthDate: child.birthDate,
           gender: child.gender,
           photoUrl: child.photoUrl,
+          photoAlt: child.photoAlt,
           medicalInfo: child.medicalInfo,
           createdAt: child.createdAt,
         },
@@ -152,6 +150,7 @@ export class ChildrenController {
           birthDate: child.birthDate,
           gender: child.gender,
           photoUrl: child.photoUrl,
+          photoAlt: child.photoAlt,
           medicalInfo: child.medicalInfo,
           createdAt: child.createdAt,
         },

maternal-app/maternal-app-backend/src/modules/children/dto/create-child.dto.ts

@@ -32,6 +32,10 @@ export class CreateChildDto {
   @IsString()
   photoUrl?: string;
 
+  @IsOptional()
+  @IsString()
+  photoAlt?: string;
+
   @IsOptional()
   @IsObject()
   medicalInfo?: Record<string, any>;