feat: FASE 2 - Client Base (layout, login, navbar, tema, i18n)

Implementazione completa del frontend Flask:
- Layout base.html con TailwindCSS CDN, dark/light theme, flash messages
- Navbar responsive role-based (Maker, MeasurementTec, Metrologist, Admin)
- Login page professionale con form + API integration
- Profilo utente: nome, lingua, tema, badge ruoli
- Sistema tema dark/light: CSS variables + Alpine.js store + localStorage
- i18n completo IT/EN: Flask-Babel (.po) + alpinejs-i18n (JSON)
- API Client riscritto: error handling normalizzato, no crash su 4xx/5xx
- CSRF protection con Flask-WTF su tutti i form
- Logo aziendale dinamico da system_settings
- Asset SVG: tmflow-logo.svg + tmflow-icon.svg (favicon)

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

client/static/img/tmflow-icon.svg

@@ -0,0 +1,27 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32" fill="none">
+  <!-- Stylized Caliper Icon for Favicon -->
+
+  <!-- Caliper outer frame -->
+  <rect x="2" y="3" width="5" height="26" rx="1.5" fill="#2563EB"/>
+  <rect x="2" y="3" width="19" height="5" rx="1.5" fill="#2563EB"/>
+  <rect x="2" y="24" width="19" height="5" rx="1.5" fill="#2563EB"/>
+
+  <!-- Sliding jaw -->
+  <rect x="12" y="8" width="4.5" height="6.5" rx="1" fill="#1E40AF"/>
+  <rect x="12" y="17.5" width="4.5" height="6.5" rx="1" fill="#1E40AF"/>
+
+  <!-- Depth rod -->
+  <rect x="4" y="14" width="12" height="3.5" rx="1" fill="#3B82F6" opacity="0.55"/>
+
+  <!-- Scale markings -->
+  <rect x="8" y="5" width="1" height="2.5" rx="0.5" fill="#FFFFFF" opacity="0.65"/>
+  <rect x="11" y="5" width="1" height="2.5" rx="0.5" fill="#FFFFFF" opacity="0.65"/>
+  <rect x="14" y="5" width="1" height="2.5" rx="0.5" fill="#FFFFFF" opacity="0.65"/>
+  <rect x="17" y="5" width="1" height="2.5" rx="0.5" fill="#FFFFFF" opacity="0.65"/>
+
+  <!-- Flow arrow -->
+  <path d="M22 16 C25 16, 26.5 11, 29 11"
+        stroke="#3B82F6" stroke-width="2.2" stroke-linecap="round" fill="none"/>
+  <path d="M27 8.5 L29.5 11 L27 13.5"
+        stroke="#3B82F6" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round" fill="none"/>
+</svg>

client/static/img/tmflow-logo.svg

@@ -0,0 +1,41 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 220 44" fill="none">
+  <!-- Stylized Caliper Icon -->
+  <g transform="translate(2, 2)">
+    <!-- Caliper outer frame -->
+    <rect x="0" y="4" width="6" height="32" rx="1.5" fill="#2563EB"/>
+    <rect x="0" y="4" width="24" height="6" rx="1.5" fill="#2563EB"/>
+    <rect x="0" y="30" width="24" height="6" rx="1.5" fill="#2563EB"/>
+
+    <!-- Caliper sliding jaw -->
+    <rect x="14" y="10" width="5" height="8" rx="1" fill="#1E40AF"/>
+    <rect x="14" y="22" width="5" height="8" rx="1" fill="#1E40AF"/>
+
+    <!-- Caliper depth rod -->
+    <rect x="2" y="18" width="16" height="4" rx="1" fill="#3B82F6" opacity="0.6"/>
+
+    <!-- Scale markings -->
+    <rect x="7" y="7" width="1" height="3" rx="0.5" fill="#FFFFFF" opacity="0.7"/>
+    <rect x="10" y="7" width="1" height="3" rx="0.5" fill="#FFFFFF" opacity="0.7"/>
+    <rect x="13" y="7" width="1" height="3" rx="0.5" fill="#FFFFFF" opacity="0.7"/>
+    <rect x="16" y="7" width="1" height="3" rx="0.5" fill="#FFFFFF" opacity="0.7"/>
+    <rect x="19" y="7" width="1" height="3" rx="0.5" fill="#FFFFFF" opacity="0.7"/>
+
+    <!-- Flow arrow (smooth curve) -->
+    <path d="M26 20 C30 20, 32 14, 36 14 C40 14, 40 20, 36 20"
+          stroke="#2563EB" stroke-width="2.5" stroke-linecap="round" fill="none"/>
+    <path d="M34 17 L37 20 L34 23" stroke="#2563EB" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" fill="none"/>
+  </g>
+
+  <!-- Text: TieMeasureFlow -->
+  <g transform="translate(48, 0)">
+    <!-- "Tie" in bold primary -->
+    <text x="0" y="28" font-family="Inter, system-ui, sans-serif" font-size="20" font-weight="700" fill="#2563EB"
+          letter-spacing="-0.5">Tie</text>
+    <!-- "Measure" in medium dark -->
+    <text x="32" y="28" font-family="Inter, system-ui, sans-serif" font-size="20" font-weight="500" fill="#1E40AF"
+          letter-spacing="-0.5">Measure</text>
+    <!-- "Flow" in bold primary -->
+    <text x="120" y="28" font-family="Inter, system-ui, sans-serif" font-size="20" font-weight="700" fill="#2563EB"
+          letter-spacing="-0.5">Flow</text>
+  </g>
+</svg>