Replace shared email commands with MediatR notifications (#280)

docs/web/diagrams/auth/registration.mmd

@@ -127,9 +127,9 @@ sequenceDiagram
             TokenSvc-->>RegHandler: Confirmation Token
             deactivate TokenSvc
 
-            RegHandler->>Mediator: Send(SendRegistrationEmailCommand) (Shared.Application cross-slice contract)
+            RegHandler->>Mediator: Publish(UserRegisteredNotification)
             activate Mediator
-            Note right of Mediator: Routed to Features.Emails' SendRegistrationEmailHandler — the second of two cross-slice dispatches in this flow (profile creation is the first)
+            Note right of Mediator: Features.Emails has a direct ProjectReference on Features.Users and handles the notification via UserRegisteredNotificationHandler — the second of two cross-slice dispatches in this flow (profile creation is the first)
             Mediator->>EmailDispatcher: SendRegistrationEmailAsync(firstName, email, confirmationToken)
             activate EmailDispatcher
 
@@ -147,15 +147,15 @@ sequenceDiagram
             SMTP-->>EmailDispatcher: Success / throws
             deactivate SMTP
             deactivate EmailDispatcher
-            deactivate Mediator
 
             alt Email sent successfully
-                RegHandler->>RegHandler: emailSent = true
-            else mediator.Send throws
-                RegHandler->>RegHandler: catch(Exception), log to stderr, emailSent = false
+                Note right of Mediator: UserRegisteredNotificationHandler completes normally
+            else EmailDispatcher throws
+                Note right of Mediator: UserRegisteredNotificationHandler catches and logs the exception — registration is unaffected
             end
+            deactivate Mediator
 
-            RegHandler-->>Mediator: RegistrationPayload(userAccountId, username, refreshToken, accessToken, confirmationEmailSent)
+            RegHandler-->>Mediator: RegistrationPayload(userAccountId, username, refreshToken, accessToken)
             deactivate RegHandler
             Mediator-->>API: RegistrationPayload
             deactivate Mediator

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

@@ -51,13 +51,20 @@ sequenceDiagram
             TokenSvc-->>ResendHandler: confirmation token
             deactivate TokenSvc
 
-            ResendHandler->>Mediator: Send(SendResendConfirmationEmailCommand)
+            ResendHandler->>Mediator: Publish(ConfirmationEmailResendRequestedNotification)
             activate Mediator
+            Note right of Mediator: Features.Emails has a direct ProjectReference on Features.Users and handles the notification via ConfirmationEmailResendRequestedNotificationHandler
             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
+
+            alt Email sent successfully
+                Note right of Mediator: ConfirmationEmailResendRequestedNotificationHandler completes normally
+            else EmailDispatcher throws
+                Note right of Mediator: ConfirmationEmailResendRequestedNotificationHandler catches and logs the exception — the resend request is unaffected
+            end
             deactivate Mediator
         end
     end

docs/web/diagrams/vertical-slice.md

@@ -16,13 +16,14 @@ doesn't wire up any slice; it applies schema directly.
 
 ## Project reference dependencies
 
-Solid arrows are compile-time project references. Dashed arrows are the two
-places slices talk to each other without a direct reference: the email MediatR
-contract routed through `Shared.Application`, and the one place that pattern is
-broken outright. Every DB-backed slice depends on the same three foundation
-projects (`Shared.Contracts`, `Domain.Entities`, `Database.Connection`) — drawn
-as one box instead of fifteen separate arrows; see the notes for what else each
-of those foundation projects pulls in.
+Solid arrows are compile-time project references — every slice-to-slice
+dependency is one now that the email MediatR contract has moved off
+`Shared.Application`: `Features.Users` on `Features.PhotoUpload` for avatar
+uploads, and `Features.Emails` on `Features.Users` for the registration and
+resend-confirmation notifications. Every DB-backed slice depends on the same
+three foundation projects (`Shared.Contracts`, `Domain.Entities`,
+`Database.Connection`) — drawn as one box instead of fifteen separate arrows;
+see the notes for what else each of those foundation projects pulls in.
 
 ```mermaid
 --8<-- "web/diagrams/vertical-slice/project-references.mmd"
@@ -54,17 +55,20 @@ of those foundation projects pulls in.
   - `Features.Beers` is scaffolded (project + references only, no source files
     yet)
 
-- **The one exception to slice isolation**: `Features.Users` takes a direct
-  project reference to `Features.PhotoUpload`
-  - sends its `UploadPhotoCommand` via MediatR from `UploadAvatarHandler`
-  - unlike the email flow, the command type lives in the target slice itself,
-    not in `Shared.Application`
+- **The exceptions to slice isolation**:
+  - `Features.Users` takes a direct project reference to `Features.PhotoUpload`
+    - sends its `UploadPhotoCommand` via MediatR from `UploadAvatarHandler`
+    - the command type lives in the target slice itself, not in
+      `Shared.Application`
+  - `Features.Emails` takes a direct project reference to `Features.Users`
+    - handles `UserRegisteredNotification` (published from
+      `RegisterUserHandler`) and `ConfirmationEmailResendRequestedNotification`
+      (published from `ResendConfirmationEmailHandler`)
+    - both notification types live in `Features.Users`
+      (`Features.Auth.Notifications`), not in `Shared.Application`
 
 - **Shared.Application**:
   - `ValidationBehavior` (MediatR pipeline)
-  - Cross-slice email commands (`SendRegistrationEmailCommand`,
-    `SendResendConfirmationEmailCommand`)
-  - MediatR command contract (not project reference)
   - Every slice (including `Features.Emails`) references it for the pipeline
     behavior alone
 

docs/web/diagrams/vertical-slice/project-references.mmd

@@ -31,8 +31,7 @@ EmailTemplates["Infrastructure.Email.Templates"]
 end
 
 UsersSlice == project ref, sends UploadPhotoCommand ==> PhotoSlice
-UsersSlice -. sends email commands .-> SharedApp["Shared.Application<br>(email command contract)"]
-EmailsSlice -. handles email commands .-> SharedApp
+EmailsSlice == project ref, handles UserRegisteredNotification & ConfirmationEmailResendRequestedNotification ==> UsersSlice
 BrewerySlice --> FOUNDATION
 LocationsSlice --> FOUNDATION
 BeersSlice --> FOUNDATION