feat: Souq native integration + auth simplification + CE-wide enhancements

Souq Marketplace:
- Native souq pages: browse+filters, create listing, detail+seller profile, orders+chat
- New API: reviews (POST), sellers/[id], upload (multipart), polar-checkout webhook
- Listings API enhanced: minPrice, maxPrice, sortBy, deliveryDays filters
- Seller workflow: start order, mark delivered, upload files, confirm delivery
- Wallet: 5 Polar.sh FLH tiers, production checkout, mock fallback, success banner
- Fix: order redirect /souq/history → /souq/orders

Auth System:
- Unified auth page, removed OAuth provider routing (2 files deleted)
- Deleted oauth.ts (319 lines) — simplified auth chain
- Streamlined login/register API routes

Prisma Schema (+179 lines):
- New models: Listing, Purchase, Review, Group/GroupMember
- Gamification: DailyStreak, XpTransaction, Achievement, UserLevel
- Learning: LearnCourse/Module/Enrollment/Certificate
- Notifications, Referrals, Dhikr, PremiumBenefits

Deleted legacy code:
- src/app/api/marketplace/* (3 files) — replaced by /api/souq/*
- src/app/api/files/[listingId]/route.ts — replaced by /api/souq/upload
- src/app/api/seller/[sellerId]/route.ts — replaced by /api/souq/sellers/[id]

Infrastructure:
- Dockerfile: standalone output, Prisma runtime migration
- docker-compose.yml: Polar env vars, healthcheck fix
- docker-compose.staging.yml: staging on port 4014
- .gitea/workflows/ci.yml: CI pipeline

src/app/api/learn/certificates/verify/[serial]/route.ts

@@ -0,0 +1,39 @@
+import { NextRequest, NextResponse } from "next/server";
+import { prisma } from "@/lib/prisma";
+
+// GET /api/learn/certificates/verify/[serial] — public verification
+export async function GET(
+  request: NextRequest,
+  { params }: { params: Promise<{ serial: string }> }
+) {
+  try {
+    const { serial } = await params;
+
+    const certificate = await prisma.learnCertificate.findUnique({
+      where: { serialNumber: serial },
+      include: {
+        course: {
+          select: { title: true },
+        },
+      },
+    });
+
+    if (!certificate) {
+      return NextResponse.json({ valid: false });
+    }
+
+    return NextResponse.json({
+      valid: !certificate.revoked,
+      serialNumber: certificate.serialNumber,
+      userName: certificate.userName,
+      courseTitle: certificate.course.title,
+      moduleCount: certificate.moduleCount,
+      score: certificate.score,
+      issuedAt: certificate.issuedAt.toISOString(),
+      revoked: certificate.revoked,
+    });
+  } catch (error) {
+    console.error("GET /api/learn/certificates/verify/[serial] error:", error);
+    return NextResponse.json({ valid: false });
+  }
+}