feat(profile): first/last name fields + collapse notification preferences

Two related cleanups for the user profile surface area:

(1) Add canonical first_name + last_name columns to user_profiles.
    Migration 0049 backfills from display_name by splitting on the
    first whitespace run; single-token names land as
    (display_name, NULL) so we never throw away existing data.
    Display name becomes an optional override (nicknames, vanity
    formatting). /api/v1/me PATCH now accepts firstName/lastName,
    and the user-settings form surfaces them as the primary inputs
    with display name as a secondary "How your name appears" field.

(2) Remove the broken Notifications card from user-settings (it called
    PATCH on an endpoint that has GET/PUT only and used a flat shape
    vs the actual array shape). Replace with the working
    NotificationPreferencesForm + ReminderDigestForm under a
    #notifications anchor. /notifications/preferences becomes a
    server-side redirect to /settings#notifications for back-compat;
    the mobile More-sheet + user-menu Bell entry now deep-link to the
    new anchor directly.

Drops the auto-generated drizzle-kit catch-up migration so we're not
sneaking accumulated schema drift into the journal — only the targeted
0049 lands here.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/api/v1/me/route.ts

@@ -9,6 +9,8 @@ import { errorResponse, NotFoundError, ValidationError } from '@/lib/errors';
 import { z } from 'zod';
 
 const updateProfileSchema = z.object({
+  firstName: z.string().min(1).max(120).nullable().optional(),
+  lastName: z.string().min(1).max(120).nullable().optional(),
   displayName: z.string().min(1).max(200).optional(),
   phone: z.string().nullable().optional(),
   // Refuse `javascript:` / `data:` schemes — z.string().url() lets them
@@ -55,7 +57,14 @@ export const GET = withAuth(async (_req, ctx: AuthContext) => {
   // round-trip on app boot.
   const profile = await db.query.userProfiles.findFirst({
     where: eq(userProfiles.userId, ctx.userId),
-    columns: { preferences: true, avatarFileId: true, avatarUrl: true },
+    columns: {
+      preferences: true,
+      avatarFileId: true,
+      avatarUrl: true,
+      firstName: true,
+      lastName: true,
+      displayName: true,
+    },
   });
 
   return NextResponse.json({
@@ -70,6 +79,9 @@ export const GET = withAuth(async (_req, ctx: AuthContext) => {
       profile: {
         avatarFileId: profile?.avatarFileId ?? null,
         avatarUrl: profile?.avatarUrl ?? null,
+        firstName: profile?.firstName ?? null,
+        lastName: profile?.lastName ?? null,
+        displayName: profile?.displayName ?? null,
       },
     },
   });
@@ -85,6 +97,8 @@ export const PATCH = withAuth(async (req, ctx: AuthContext) => {
     if (!profile) throw new NotFoundError('profile');
 
     const updates: Record<string, unknown> = { updatedAt: new Date() };
+    if (body.firstName !== undefined) updates.firstName = body.firstName;
+    if (body.lastName !== undefined) updates.lastName = body.lastName;
     if (body.displayName !== undefined) updates.displayName = body.displayName;
     if (body.phone !== undefined) updates.phone = body.phone;
     if (body.avatarUrl !== undefined) updates.avatarUrl = body.avatarUrl;
@@ -119,6 +133,8 @@ export const PATCH = withAuth(async (req, ctx: AuthContext) => {
     return NextResponse.json({
       data: {
         userId: updated!.userId,
+        firstName: updated!.firstName,
+        lastName: updated!.lastName,
         displayName: updated!.displayName,
         phone: updated!.phone,
         avatarUrl: updated!.avatarUrl,