Refactor documentation and diagrams for web/pipeline. (#272)

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com> for assistance with diagram creation and documentation prose updates.

docs/web/diagrams/auth/resend-confirmation.mmd

@@ -0,0 +1,71 @@
+sequenceDiagram
+    actor User
+    participant API as API Controller
+    participant Mediator as MediatR pipeline<br/>(ValidationBehavior)
+    box Handler Layer
+        participant ResendHandler as ResendConfirmationEmailHandler
+        participant UserMgr as UserManager(ApplicationUser)
+        participant TokenSvc as TokenService
+    end
+    box Infrastructure Layer
+        participant SMTP as Email Provider
+        participant Template as Template Provider
+    end
+    box Repository / Cross-slice
+        participant UserStore as DapperUserStore<br/>(IUserStore/IUserPasswordStore/IUserEmailStore)
+        participant EmailDispatcher as EmailDispatcher<br/>(Features.Emails)
+    end
+    participant DB as SQL Server
+
+    User->>API: POST /api/auth/confirm/resend?userId={id} (requires Bearer access token)
+    activate API
+    API->>Mediator: Send(ResendConfirmationEmailCommand(userId))
+    activate Mediator
+    Mediator->>ResendHandler: Handle(command)
+    activate ResendHandler
+
+    ResendHandler->>UserMgr: FindByIdAsync(userId)
+    activate UserMgr
+    UserMgr->>UserStore: FindByIdAsync(userId)
+    activate UserStore
+    UserStore->>DB: SELECT ... FROM UserAccount WHERE UserAccountID = @Id
+    activate DB
+    DB-->>UserStore: row or null
+    deactivate DB
+    UserStore-->>UserMgr: ApplicationUser or null
+    deactivate UserStore
+    UserMgr-->>ResendHandler: ApplicationUser or null
+    deactivate UserMgr
+
+    alt User not found
+        ResendHandler->>ResendHandler: return silently (prevents user enumeration)
+    else User found
+        ResendHandler->>UserMgr: IsEmailConfirmedAsync(user)
+        UserMgr-->>ResendHandler: bool
+
+        alt Already confirmed
+            ResendHandler->>ResendHandler: return silently (no-op)
+        else Not yet confirmed
+            ResendHandler->>TokenSvc: GenerateConfirmationToken(user)
+            activate TokenSvc
+            TokenSvc-->>ResendHandler: confirmation token
+            deactivate TokenSvc
+
+            ResendHandler->>Mediator: Send(SendResendConfirmationEmailCommand)
+            activate Mediator
+            Mediator->>EmailDispatcher: SendResendConfirmationEmailAsync(firstName, email, confirmationToken)
+            activate EmailDispatcher
+            EmailDispatcher->>Template: Render email (same Razor pipeline as registration)
+            EmailDispatcher->>SMTP: SendAsync(email, subject, body)
+            deactivate EmailDispatcher
+            deactivate Mediator
+        end
+    end
+
+    ResendHandler-->>Mediator: (void)
+    deactivate ResendHandler
+    Mediator-->>API: (void)
+    deactivate Mediator
+    API->>User: 200 OK {message: "confirmation email has been resent"}
+    Note right of API: Always 200 OK regardless of outcome above — same user-enumeration precaution as a not-found user or an already-confirmed account
+    deactivate API