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/acquisti.html

@@ -0,0 +1,42 @@
+{% extends "base.html" %}
+{% block title %}Acquisti - Mago4 Demo{% endblock %}
+{% block window_tabs %}<a href="/acquisti" class="window-tab active"><i class="material-icons">shopping_cart</i> Acquisti</a>{% endblock %}
+
+{% block content %}
+<div class="module-bar">
+    <div class="module-title">Acquisti</div>
+    <div class="breadcrumb"><a href="/">Mago4</a><span class="sep">»</span><span class="current">Acquisti</span></div>
+</div>
+<div class="tab-strip">
+    <a href="/purchase-orders">Ordini Fornitore</a>
+    <a href="/acquisti" class="active">Documenti Acquisto</a>
+    <a href="#">Politiche Acquisto</a>
+</div>
+
+<div class="cards-grid">
+    <div class="menu-card">
+        <div class="menu-card-header"><h3>Ordini Fornitore</h3><span class="collapse-dot">○—</span></div>
+        <div class="menu-card-body">
+            <a href="/purchase-orders" class="menu-link"><i class="material-icons ml-icon mtype-form">shopping_cart</i><span class="ml-text">Ordini Fornitore</span><i class="material-icons ml-star">star_border</i></a>
+            <a href="/purchase-orders" class="menu-link"><i class="material-icons ml-icon mtype-list">list_alt</i><span class="ml-text">Lista Ordini Fornitore</span><i class="material-icons ml-star">star_border</i></a>
+            <a href="/purchase-orders" class="menu-link"><i class="material-icons ml-icon mtype-print">print</i><span class="ml-text">Portafoglio Fornitori</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 Acquisto</h3><span class="collapse-dot">○—</span></div>
+        <div class="menu-card-body">
+            <a href="#" class="menu-link"><i class="material-icons ml-icon mtype-form">receipt_long</i><span class="ml-text">Fatture di Acquisto</span><i class="material-icons ml-star">star_border</i></a>
+            <a href="#" class="menu-link"><i class="material-icons ml-icon mtype-form">inventory</i><span class="ml-text">Documenti di Carico</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="/magazzino" class="menu-link"><i class="material-icons ml-icon mtype-proc">bolt</i><span class="ml-text">Generazione Ordini da Sottoscorta</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">Statistiche Acquisti</span><i class="material-icons ml-star">star_border</i></a>
+        </div>
+    </div>
+</div>
+{% endblock %}