fix(auth/mobile): support LAN-IP access in dev + edge-to-edge auth bg

- branded-auth-shell: split the background image into a separate
    fixed-positioned layer behind the layout. Previously the bg was on
    a min-h-screen container and iOS Safari left visible whitespace at
    the top/bottom when the URL bar showed/hid (the container's height
    didn't match the visual viewport). Now the bg pins to the actual
    visible viewport via `fixed inset-0`. min-h-[100dvh] also added
    so the layout layer matches.
  - auth client: derive baseURL from window.location.origin instead of
    NEXT_PUBLIC_APP_URL. Same dev build now works whether opened on
    localhost (Mac) or the LAN IP (iPhone on Wi-Fi).
  - auth server: dynamic trustedOrigins function that allows
    localhost / 127.x / 192.168.x / 10.x in dev (function form
    inspects the incoming request's Origin). Production stays locked
    to NEXT_PUBLIC_APP_URL.
  - new dev helper: scripts/dev-set-password.ts to set a user's
    better-auth password directly (bypasses the email-reset flow);
    used to bootstrap matt@letsbe.solutions for mobile testing.

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

scripts/dev-set-password.ts

@@ -0,0 +1,40 @@
+/**
+ * Dev helper: set a user's password directly (bypasses email reset).
+ * Usage: pnpm tsx scripts/dev-set-password.ts <email> <password>
+ */
+import 'dotenv/config';
+import { hashPassword } from 'better-auth/crypto';
+import { eq, and } from 'drizzle-orm';
+import { db } from '@/lib/db';
+import { user, account } from '@/lib/db/schema/users';
+
+async function main() {
+  const [, , email, password] = process.argv;
+  if (!email || !password) {
+    console.error('Usage: pnpm tsx scripts/dev-set-password.ts <email> <password>');
+    process.exit(1);
+  }
+
+  const u = await db.query.user.findFirst({ where: eq(user.email, email) });
+  if (!u) {
+    console.error(`User not found: ${email}`);
+    process.exit(1);
+  }
+
+  const hash = await hashPassword(password);
+  const result = await db
+    .update(account)
+    .set({ password: hash, updatedAt: new Date() })
+    .where(and(eq(account.userId, u.id), eq(account.providerId, 'credential')))
+    .returning({ id: account.id });
+
+  if (result.length === 0) {
+    console.error(`No credential account row for ${email}`);
+    process.exit(1);
+  }
+
+  console.log(`Updated password for ${email} (account id ${result[0]?.id}).`);
+  process.exit(0);
+}
+
+main();