feat(notifications): settings UI for per-workflow opt-out (audit §9.3 #14 follow-on)

Lands the user-facing half of the unsubscribe preferences work. The
one-click endpoint already shipped in this PR's main commit; this adds
the proactive self-service path at /dashboard/settings?tab=notifications
so users don't have to wait for a mail to land before tuning their
preferences.

Backend
-------
New EmailPreferencesController at /api/email/preferences:
  GET  → returns one row per OPTIONAL_WORKFLOWS entry, each with current
         optedOut boolean (false when no DB row exists).
  POST → body {workflow, optedOut} flips the row; source='settings_page'
         captured for the audit trail.
Auth+payment workflows are deliberately not exposed — the server's
OPTIONAL_WORKFLOWS set stays the single source of truth.

Frontend
--------
Adds a 'notifications' tab to /dashboard/settings (between 'preferences'
and 'security'). One toggle row per optional workflow with TR copy that
explains what each mail is for. Optimistic update — switch flips
instantly and reverts on failure; PostHog event captures accept/reject.

Static footer note clarifies that auth + payment mail keeps coming
regardless of the switches above (so users don't think they've
unsubscribed from password-reset).

i18n
----
Added settings.tabs.notifications + settings.notifications.{title,
description} to both tr.json and en.json. Body copy is hard-coded TR
(matches audit §9.3 #11 TR-only decision).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/api/src/notifications/email-preferences.controller.ts

@@ -0,0 +1,67 @@
+import { BadRequestException, Body, Controller, Get, Logger, Post } from "@nestjs/common";
+import { CurrentUser } from "../common/decorators/current-user.decorator";
+import {
+  EmailPreferencesService,
+  OPTIONAL_WORKFLOWS,
+} from "./email-preferences.service";
+
+/**
+ * Authenticated self-service preferences endpoint — paired with
+ * UnsubscribeController which handles the unauthenticated one-click flow.
+ *
+ *  GET  /api/email/preferences           — current state (all optional
+ *                                          workflows, with `optedOut: bool`).
+ *  POST /api/email/preferences           — body `{workflow, optedOut}`;
+ *                                          true → insert opt-out row,
+ *                                          false → delete it.
+ *
+ * Backs the `/dashboard/settings?tab=notifications` UI. Auth and payment
+ * workflows are deliberately not exposed: they're transactional and the
+ * service-level `OPTIONAL_WORKFLOWS` set is the single source of truth.
+ */
+@Controller("email/preferences")
+export class EmailPreferencesController {
+  private readonly logger = new Logger(EmailPreferencesController.name);
+
+  constructor(private readonly preferences: EmailPreferencesService) {}
+
+  /**
+   * Returns the per-workflow opt-out state for the calling user. Always
+   * includes every optional workflow — caller renders one row per — so a
+   * missing DB row is just `{optedOut: false}`.
+   */
+  @Get()
+  async list(
+    @CurrentUser() user: { id: string },
+  ): Promise<Array<{ workflow: string; optedOut: boolean }>> {
+    const workflows = Array.from(OPTIONAL_WORKFLOWS);
+    const optedOutFlags = await Promise.all(
+      workflows.map((w) => this.preferences.isOptedOut(user.id, w)),
+    );
+    return workflows.map((workflow, i) => ({ workflow, optedOut: optedOutFlags[i] }));
+  }
+
+  /** Toggle a single workflow's opt-out state from the settings UI. */
+  @Post()
+  async update(
+    @CurrentUser() user: { id: string },
+    @Body() body: { workflow?: string; optedOut?: boolean },
+  ): Promise<{ workflow: string; optedOut: boolean }> {
+    const { workflow, optedOut } = body;
+    if (!workflow || typeof workflow !== "string" || !OPTIONAL_WORKFLOWS.has(workflow)) {
+      throw new BadRequestException("invalid workflow");
+    }
+    if (typeof optedOut !== "boolean") {
+      throw new BadRequestException("optedOut must be boolean");
+    }
+    if (optedOut) {
+      await this.preferences.optOut(user.id, workflow, "settings_page");
+    } else {
+      await this.preferences.optIn(user.id, workflow);
+    }
+    this.logger.log(
+      `[email-prefs] user=${user.id} workflow=${workflow} → ${optedOut ? "opt-out" : "opt-in"}`,
+    );
+    return { workflow, optedOut };
+  }
+}

apps/api/src/notifications/notifications.module.ts

@@ -1,5 +1,6 @@
 import { Global, Module } from "@nestjs/common";
 import { DatabaseModule } from "../database/database.module";
+import { EmailPreferencesController } from "./email-preferences.controller";
 import { EmailPreferencesService } from "./email-preferences.service";
 import { NovuService } from "./novu.service";
 import { UnsubscribeController } from "./unsubscribe.controller";
@@ -13,7 +14,7 @@ import { UnsubscribeController } from "./unsubscribe.controller";
 @Global()
 @Module({
   imports: [DatabaseModule],
-  controllers: [UnsubscribeController],
+  controllers: [UnsubscribeController, EmailPreferencesController],
   providers: [NovuService, EmailPreferencesService],
   exports: [NovuService, EmailPreferencesService],
 })