fix(labs): unique preview for hydrostatics (was duplicate of dynamics)

Hydrostatics использовал P_SANDBOX как у dynamics — оба показывали одну
и ту же карточку с блоком/шаром и силами. Добавлен P_HYDRO: мензурка
с погруженным телом + F_A, U-образный манометр с Δh, сообщающиеся сосуды.

frontend/js/labs/lab-glue.js

@@ -351,6 +351,38 @@
     <text x="225" y="63" font-size="8" fill="#7BF5A4" font-family="monospace">F₂</text>
     <text x="135" y="133" font-size="8" fill="rgba(255,255,255,0.35)" text-anchor="middle" font-family="Manrope,sans-serif">Песочница сил · F = ma</text>`);
 
+  const P_HYDRO = _svg(`
+    <rect width="270" height="140" fill="#0D0D1A"/>
+    ${_grid('rgba(255,255,255,0.03)')}
+    <!-- left tall beaker with water + submerged body -->
+    <path d="M 38,30 L 38,118 Q 38,124 44,124 L 96,124 Q 102,124 102,118 L 102,30" fill="none" stroke="rgba(255,255,255,0.45)" stroke-width="1.6"/>
+    <rect x="40" y="56" width="60" height="66" rx="2" fill="rgba(41,121,255,0.32)"/>
+    <path d="M 40,56 Q 55,52 70,56 T 100,56 L 100,60 L 40,60 Z" fill="rgba(76,201,240,0.55)"/>
+    <text x="70" y="48" font-size="7.5" fill="rgba(76,201,240,0.9)" text-anchor="middle" font-family="monospace">P = ρgh</text>
+    <!-- submerged cube + buoyancy arrow up -->
+    <rect x="55" y="80" width="28" height="22" rx="3" fill="rgba(255,209,102,0.55)" stroke="#FFD166" stroke-width="1.4"/>
+    <line x1="69" y1="80" x2="69" y2="62" stroke="#7BF5A4" stroke-width="2.2" marker-end="url(#hb)"/>
+    <text x="79" y="72" font-size="7.5" fill="#7BF5A4" font-family="monospace">F_A</text>
+    <!-- U-tube manometer right -->
+    <path d="M 150,40 L 150,108 Q 150,116 158,116 L 198,116 Q 206,116 206,108 L 206,40" fill="none" stroke="rgba(255,255,255,0.45)" stroke-width="1.6"/>
+    <path d="M 152,80 L 168,80 L 168,114 L 188,114 L 188,68 L 204,68 L 204,80" fill="none" stroke="none"/>
+    <rect x="152" y="80" width="16" height="34" fill="rgba(76,201,240,0.55)"/>
+    <rect x="188" y="68" width="16" height="46" fill="rgba(76,201,240,0.55)"/>
+    <line x1="168" y1="80" x2="188" y2="68" stroke="rgba(76,201,240,0.55)" stroke-width="6" stroke-linecap="round"/>
+    <line x1="172" y1="80" x2="184" y2="80" stroke="rgba(255,209,102,0.7)" stroke-width="1" stroke-dasharray="2 2"/>
+    <line x1="192" y1="68" x2="204" y2="68" stroke="rgba(255,209,102,0.7)" stroke-width="1" stroke-dasharray="2 2"/>
+    <text x="178" y="36" font-size="7.5" fill="rgba(76,201,240,0.9)" text-anchor="middle" font-family="monospace">Δh</text>
+    <line x1="178" y1="38" x2="178" y2="66" stroke="rgba(255,209,102,0.85)" stroke-width="1.2" marker-end="url(#hb)"/>
+    <!-- communicating vessels (small inline icon) -->
+    <path d="M 224,80 L 224,116 L 258,116 L 258,52" fill="none" stroke="rgba(255,255,255,0.45)" stroke-width="1.4"/>
+    <rect x="226" y="100" width="6" height="14" fill="rgba(76,201,240,0.55)"/>
+    <rect x="250" y="100" width="6" height="14" fill="rgba(76,201,240,0.55)"/>
+    <line x1="232" y1="114" x2="250" y2="114" stroke="rgba(76,201,240,0.55)" stroke-width="3" stroke-linecap="round"/>
+    <defs>
+      <marker id="hb" markerWidth="7" markerHeight="7" refX="5" refY="3.5" orient="auto"><path d="M0,0 L7,3.5 L0,7 Z" fill="#7BF5A4"/></marker>
+    </defs>
+    <text x="135" y="135" font-size="7.5" fill="rgba(255,255,255,0.4)" text-anchor="middle" font-family="Manrope,sans-serif">Архимед · Паскаль · капиллярность</text>`);
+
   /* ── coming soon chem previews (simple) ── */
   const P_KINETICS = _svg(`
     <rect width="270" height="140" fill="#0D0D1A"/>
@@ -686,7 +718,7 @@
     { id: 'hydrostatics', cat: 'phys',
       title: 'Гидростатика',
       desc: 'Давление жидкости P=ρgh, закон Архимеда, сообщающиеся сосуды, поверхностное натяжение и капиллярность.',
-      preview: P_SANDBOX },
+      preview: P_HYDRO },
     { id: 'dynamics', cat: 'phys',
       title: 'Динамика',
       desc: 'Законы Ньютона, песочница сил, наклонная плоскость — всё в одном интерактивном модуле.',