feat(phase-1): TapTrack Hub initial scaffold

Full project scaffold for TapTrack Hub — cloud SaaS control plane
for managing on-prem TapTrack school deployments.

## Infrastructure
- Docker Compose: backend (gunicorn+uvicorn), Celery worker + beat,
  frontend (Vite build + nginx), PostgreSQL 15, Redis 7, nginx proxy
- Dockerfile for backend and frontend, nginx reverse proxy config

## Backend (FastAPI + SQLAlchemy async + Celery)
Database schema (10 tables):
  hub_users, schools, licenses, sms_jobs, sms_credit_ledger,
  invoices, invoice_line_items, school_subscriptions,
  support_tickets, ticket_replies, audit_logs, announcements

Auth: JWT (python-jose) + bcrypt + role-based FastAPI dependencies
  (get_current_user, require_super_admin, require_school_admin)

Routers (11): auth, schools, licenses, sms, billing, tickets,
  users, dashboard, school_portal, announcements, sync

Celery tasks (6):
  sms.process_queue, billing.generate_monthly_invoices,
  billing.send_invoice_email, billing.check_overdue,
  license.check_expiry, reports.send_monthly_reports

Services: SMTP email helper (smtplib + Jinja2)
Seed script: creates super admin admin@taptrack.io

## Frontend (Vue 3 + Vite + Pinia + Tailwind CSS)
Router: 14 routes across super admin + school portal layouts
Stores: Pinia auth store with localStorage persistence
API client: full axios client for all backend endpoints
Layouts: AppLayout (super admin), PortalLayout (school), AuthLayout
Components: AppSidebar, PortalSidebar, SidebarItem, KpiCard,
  StatusBadge, ToastStack
Pages: Login, Dashboard, Schools, SchoolDetail, Licenses, SMS,
  Billing, Tickets, TicketDetail, Users, Announcements, 404
Portal pages: Overview, Billing, SMS Reports, Tickets, Profile

## PAUL Planning Files
- .paul/ROADMAP.md: full 15-phase roadmap with detailed scope
- .paul/STATE.md: current position, tech stack, architecture notes
- .paul/phases/01-setup/01-PLAN.md: complete Phase 1 plan (done)
- .paul/phases/02 through 15: README stubs for all future phases

backend/app/tasks/billing.py

@@ -0,0 +1,125 @@
+"""Celery tasks: invoice generation, email, overdue checks."""
+import logging
+from datetime import date, timedelta
+
+from app.worker import celery_app
+
+logger = logging.getLogger(__name__)
+
+def _make_session():
+    import os
+    from sqlalchemy import create_engine
+    from sqlalchemy.orm import sessionmaker
+    db_url = os.getenv("DATABASE_URL", "postgresql://postgres:postgres@db:5432/taptrack_hub")
+    engine = create_engine(db_url.replace("postgresql+asyncpg://", "postgresql://"), pool_pre_ping=True)
+    return sessionmaker(bind=engine)()
+
+@celery_app.task(name="billing.generate_monthly_invoices")
+def generate_monthly_invoices():
+    """On the 1st: create draft invoices for all active schools with a subscription."""
+    from app.models.billing import Invoice, SchoolSubscription, InvoiceLineItem, BillingCycle
+    from app.models.school import School, SchoolStatus
+    from sqlalchemy import select
+    from datetime import date
+
+    db = _make_session()
+    try:
+        today = date.today()
+        period_start = date(today.year, today.month, 1)
+        prev_month = (period_start - timedelta(days=1))
+        billing_start = date(prev_month.year, prev_month.month, 1)
+        billing_end = period_start - timedelta(days=1)
+
+        subs = db.execute(select(SchoolSubscription).where(SchoolSubscription.is_active == True)).scalars().all()
+        count = db.execute(select(func.count()).select_from(Invoice)).scalar_one()
+
+        for sub in subs:
+            school = db.get(School, sub.school_id)
+            if not school or school.status != SchoolStatus.active:
+                continue
+            total = float(sub.monthly_fee)
+            inv_num = f"INV-{billing_start.strftime('%Y%m')}-{count + 1:04d}"
+            count += 1
+            inv = Invoice(
+                school_id=sub.school_id,
+                invoice_number=inv_num,
+                billing_period_start=billing_start,
+                billing_period_end=billing_end,
+                subscription_amount=float(sub.monthly_fee),
+                total_amount=total,
+                due_date=period_start + timedelta(days=14),
+            )
+            db.add(inv)
+            db.flush()
+            db.add(InvoiceLineItem(
+                invoice_id=inv.id,
+                description=f"Monthly subscription — {school.name}",
+                quantity=1,
+                unit_price=float(sub.monthly_fee),
+                amount=float(sub.monthly_fee),
+            ))
+        db.commit()
+        logger.info(f"Generated {len(subs)} invoices for {billing_start}")
+    except Exception as e:
+        db.rollback()
+        logger.error(f"generate_monthly_invoices error: {e}")
+    finally:
+        db.close()
+
+@celery_app.task(name="billing.send_invoice_email")
+def send_invoice_email_task(invoice_id: str):
+    """Send invoice email to school billing contact."""
+    from app.models.billing import Invoice, InvoiceStatus
+    from app.models.school import School
+    from app.services.email import send_email
+    from sqlalchemy import select
+
+    db = _make_session()
+    try:
+        inv = db.get(Invoice, invoice_id)
+        if not inv:
+            return
+        school = db.get(School, inv.school_id)
+        if not school or not school.billing_email:
+            return
+        body = f"""Dear {school.contact_name or school.name},
+
+Please find your invoice {inv.invoice_number} for the period {inv.billing_period_start} to {inv.billing_period_end}.
+
+Amount Due: PHP {float(inv.total_amount):,.2f}
+Due Date: {inv.due_date}
+
+Please log in to your TapTrack Hub portal to view and pay your invoice.
+
+Thank you,
+TapTrack Hub Team
+"""
+        send_email(to=school.billing_email, subject=f"Invoice {inv.invoice_number} — TapTrack Hub", body=body)
+        from datetime import datetime, timezone
+        inv.email_sent_at = datetime.now(timezone.utc)
+        if inv.status.value == "draft":
+            inv.status = InvoiceStatus.sent
+        db.commit()
+    finally:
+        db.close()
+
+@celery_app.task(name="billing.check_overdue")
+def check_overdue():
+    """Mark overdue invoices and send warning emails."""
+    from app.models.billing import Invoice, InvoiceStatus
+    from sqlalchemy import select, and_
+
+    db = _make_session()
+    try:
+        today = date.today()
+        overdue = db.execute(
+            select(Invoice).where(
+                and_(Invoice.status == InvoiceStatus.sent, Invoice.due_date < today, Invoice.due_date != None)
+            )
+        ).scalars().all()
+        for inv in overdue:
+            inv.status = InvoiceStatus.overdue
+        db.commit()
+        logger.info(f"Marked {len(overdue)} invoices as overdue")
+    finally:
+        db.close()