feat(auth): adds basic endpoints: register, login, forgot password, reset password

docs/architecture.md

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+# TrakQR Architecture Guidelines
+
+## Core Principles
+
+### 1. Modular Monolith
+The application is structured as a modular monolith where each feature/domain is self-contained but runs in a single deployable unit.
+
+This provides:
+- Clear boundaries between features
+- Easy refactoring to microservices if needed later
+- Simplified deployment and operations
+
+### 2. Vertical Slice Architecture
+Code is organized by **feature** (vertical slices), not by technical layer (horizontal).
+
+Each feature contains everything it needs:
+- Endpoint definitions
+- Request/Response models
+- Business logic
+- Validators
+
+```
+/Features
+  /Auth
+    /Endpoints
+      SmallEndpoint.cs (contains Request, Response, Validator and Endpoint)
+    /Register
+      Endpoint.cs
+      Request.cs
+      Response.cs
+      Validator.cs
+    /Login
+      ...
+  /Links
+    /Create
+      ...
+    /List
+      ...
+  /QRCodes
+    ...
+```
+
+### 3. Minimal API with FastEndpoints
+We use [FastEndpoints](https://fast-endpoints.com/) instead of traditional MVC Controllers because:
+- Better performance (no reflection-based model binding)
+- Cleaner, more focused endpoint classes
+- Built-in validation with FluentValidation
+- Request/Response DTOs are co-located with endpoints
+- Easier testing
+
+### 4. No Traditional Controllers
+**DO NOT** use `[ApiController]` or `ControllerBase`. All HTTP endpoints must be FastEndpoints.
+
+## Module Structure
+
+Each feature module should be **fully self-contained**. All code related to a feature lives within that feature's folder:
+
+```
+/Features/{Module}/
+  - {Module}Responses.cs   # Shared response DTOs for this module
+  - {Module}Settings.cs    # Configuration classes for this module
+  /{Operation}/
+    - Endpoint.cs          # The FastEndpoint class
+    - Request.cs           # Input DTO
+    - Validator.cs         # FluentValidation rules
+```
+
+**Example - Auth module:**
+```
+/Features/Auth/
+  - AuthResponses.cs       # AuthResponse, UserInfo, MessageResponse
+  - JwtSettings.cs         # JWT configuration
+  /Register/
+    - Endpoint.cs
+    - Request.cs
+    - Validator.cs
+  /Login/
+    - Endpoint.cs
+    - Request.cs
+    - Validator.cs
+```
+
+For simple operations, business logic lives directly in the Endpoint class. For complex logic, add a `Handler.cs` or `Service.cs` within the same feature folder.
+
+## Shared Infrastructure
+
+Only truly cross-cutting infrastructure goes outside Features:
+- `/Data` - DbContext, migrations (shared database access)
+- `/Models` - EF Core entities (shared domain model)
+
+## Dependency Injection
+
+- Use constructor injection
+- Register services in `Program.cs` or feature-specific extension methods
+- Prefer scoped services for request-specific work
+
+## Validation
+
+- Use FluentValidation via FastEndpoints' built-in support
+- Validate at the endpoint level, not in services
+- Return 400 Bad Request with structured error responses
+
+## Authentication
+
+- JWT Bearer tokens for API authentication
+- Claims-based authorization
+- User ID extracted from JWT `sub` claim