Restyle UI to match Mago4 and add invoicing, warehouse, scadenzario

Rework the demo into a faithful Mago4 look-and-feel and expand it with
core ERP modules modelled on the real Mago4 database schema.

UI (ispirata a Mago4):
- Blue header with logo/search/operation date, desktop-style window tabs
- White sidebar with coloured module icons (Anagrafiche, Vendite, Acquisti,
  Amministrazione, Logistica)
- Card-based module landing pages with breadcrumb + tab strip
- Document detail forms with left tabs, line grid and totals box

Fatturazione (InvoiceMng / MA_SaleDoc):
- Document types (Fattura Immediata, DDT, Nota di Credito, ProForma)
- Lines with discount/IVA, automatic taxable/tax/total computation
- Document states (draft -> printed -> issued / posted_to_inventory)

Magazzino (Inventory / MA_InventoryEntries + MA_InventoryReasons):
- Inventory movements with load/unload reasons (DebitCreditSign)
- Posting a movement actually updates item balances
- Causali and stock valuation pages

Amministrazione / Scadenzario (AP_AR / MA_PyblsRcvbls):
- Open items (receivables/payables) with due date, method, state
- Settle action closes the item and recomputes the cash forecast

Dashboard riprogettata (focus su scadenze e to-do):
- Overdue alert banner, KPI for overdue payables/receivables
- Upcoming deadlines table, prioritised "Cose da fare" action list
- 30-day cash-flow forecast and customer credit-limit check

Adds REST endpoints for invoices, movements, schedules and dashboard data.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/vendite.html

@@ -0,0 +1,53 @@
+{% extends "base.html" %}
+{% block title %}Vendite - Mago4 Demo{% endblock %}
+{% block window_tabs %}<a href="/vendite" class="window-tab active"><i class="material-icons">point_of_sale</i> Vendite</a>{% endblock %}
+
+{% block content %}
+<div class="module-bar">
+    <div class="module-title">Documenti Vendita</div>
+    <div class="breadcrumb"><a href="/">Mago4</a><span class="sep">»</span><a href="/vendite">Vendite</a><span class="sep">»</span><span class="current">Documenti Vendita</span></div>
+</div>
+<div class="tab-strip">
+    <a href="/sales-orders">Ordini Cliente</a>
+    <a href="/vendite" class="active">Documenti Vendita</a>
+    <a href="#">Politiche Vendita</a>
+    <a href="#">Statistiche</a>
+</div>
+
+<div class="cards-grid">
+    <div class="menu-card">
+        <div class="menu-card-header"><h3>Fatture</h3><span class="collapse-dot">○—</span></div>
+        <div class="menu-card-body">
+            <a href="/invoices?type=immediate_invoice" class="menu-link"><i class="material-icons ml-icon mtype-form">request_quote</i><span class="ml-text">Fatture Immediate</span><i class="material-icons ml-star">star_border</i></a>
+            <a href="/invoices?type=accompanying_invoice" class="menu-link"><i class="material-icons ml-icon mtype-form">receipt</i><span class="ml-text">Fatture Accompagnatorie</span><i class="material-icons ml-star">star_border</i></a>
+            <a href="/invoices?type=proforma_invoice" class="menu-link"><i class="material-icons ml-icon mtype-list">description</i><span class="ml-text">Fatture ProForma</span><i class="material-icons ml-star">star_border</i></a>
+            <a href="/invoices" class="menu-link"><i class="material-icons ml-icon mtype-print">print</i><span class="ml-text">Portafoglio Clienti</span><i class="material-icons ml-star">star_border</i></a>
+        </div>
+    </div>
+
+    <div class="menu-card">
+        <div class="menu-card-header"><h3>Documenti di Trasporto</h3><span class="collapse-dot">○—</span></div>
+        <div class="menu-card-body">
+            <a href="/invoices?type=delivery_note" class="menu-link"><i class="material-icons ml-icon mtype-form">local_shipping</i><span class="ml-text">Documenti di Trasporto</span><i class="material-icons ml-star">star_border</i></a>
+            <a href="/invoices?type=delivery_note" class="menu-link"><i class="material-icons ml-icon mtype-list">list_alt</i><span class="ml-text">Lista Documenti di Trasporto</span><i class="material-icons ml-star">star_border</i></a>
+        </div>
+    </div>
+
+    <div class="menu-card">
+        <div class="menu-card-header"><h3>Note di Credito / Debito</h3><span class="collapse-dot">○—</span></div>
+        <div class="menu-card-body">
+            <a href="/invoices?type=credit_note" class="menu-link"><i class="material-icons ml-icon mtype-form">undo</i><span class="ml-text">Note di Credito</span><i class="material-icons ml-star">star_border</i></a>
+            <a href="/invoices?type=debit_note" class="menu-link"><i class="material-icons ml-icon mtype-form">redo</i><span class="ml-text">Note di Debito</span><i class="material-icons ml-star">star_border</i></a>
+        </div>
+    </div>
+
+    <div class="menu-card">
+        <div class="menu-card-header"><h3>Procedure</h3><span class="collapse-dot">○—</span></div>
+        <div class="menu-card-body">
+            <a href="#" class="menu-link"><i class="material-icons ml-icon mtype-proc">bolt</i><span class="ml-text">Fatturazione Differita DDT</span><i class="material-icons ml-star">star_border</i></a>
+            <a href="#" class="menu-link"><i class="material-icons ml-icon mtype-proc">bolt</i><span class="ml-text">Evasione Picking List</span><i class="material-icons ml-star">star_border</i></a>
+            <a href="#" class="menu-link"><i class="material-icons ml-icon mtype-print">bar_chart</i><span class="ml-text">Grafici di Fatturato</span><i class="material-icons ml-star">star_border</i></a>
+        </div>
+    </div>
+</div>
+{% endblock %}