feat(backend): Implement Refresh Token mechanism (Day 5 Phase 1)

Implemented secure refresh token rotation with the following features:
- RefreshToken domain entity with IsExpired(), IsRevoked(), IsActive(), Revoke() methods
- IRefreshTokenService with token generation, rotation, and revocation
- RefreshTokenService with SHA-256 hashing and token family tracking
- RefreshTokenRepository for database operations
- Database migration for refresh_tokens table with proper indexes
- Updated LoginCommandHandler and RegisterTenantCommandHandler to return refresh tokens
- Added POST /api/auth/refresh endpoint (token rotation)
- Added POST /api/auth/logout endpoint (revoke single token)
- Added POST /api/auth/logout-all endpoint (revoke all user tokens)
- Updated JWT access token expiration to 15 minutes (from 60)
- Refresh token expiration set to 7 days
- Security features: token reuse detection, IP address tracking, user-agent logging

Changes:
- Domain: RefreshToken.cs, IRefreshTokenRepository.cs
- Application: IRefreshTokenService.cs, updated LoginResponseDto and RegisterTenantResult
- Infrastructure: RefreshTokenService.cs, RefreshTokenRepository.cs, RefreshTokenConfiguration.cs
- API: AuthController.cs (3 new endpoints), RefreshTokenRequest.cs, LogoutRequest.cs
- Configuration: appsettings.Development.json (updated JWT settings)
- DI: DependencyInjection.cs (registered new services)
- Migration: AddRefreshTokens migration

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

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

colaflow-api/src/ColaFlow.API/ColaFlow.API.csproj

@@ -7,6 +7,7 @@
   </PropertyGroup>
 
   <ItemGroup>
+    <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="9.0.10" />
     <PackageReference Include="Microsoft.AspNetCore.OpenApi" Version="9.0.9" />
     <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="9.0.0">
       <PrivateAssets>all</PrivateAssets>