feat: Add weather foreground option (experimental)

- Add weatherEffectsForeground setting to render weather effects in front of chat
- Add UI toggle in main panel (visible when Dynamic Weather toggle is visible)
- Apply z-index 9998 when foreground option is enabled
- Fix weather container sizing with viewport units (100vh/100dvh) for better mobile support

template.html

@@ -125,6 +125,14 @@
                         <span class="rpg-toggle-text" data-i18n-key="template.mainPanel.dynamicWeatherEffects">Dynamic Weather</span>
                     </label>
                 </div>
+                <!-- Weather Foreground Toggle (Experimental) -->
+                <div class="rpg-toggle-container rpg-feature-col" id="rpg-weather-foreground-toggle-wrapper">
+                    <label class="rpg-toggle-label" title="Weather Effects in Foreground (Experimental)">
+                        <input type="checkbox" id="rpg-toggle-weather-foreground">
+                        <i class="fa-solid fa-layer-group"></i>
+                        <span class="rpg-toggle-text">Weather Foreground</span>
+                    </label>
+                </div>
                 <!-- Narrator Mode Toggle -->
                 <div class="rpg-toggle-container rpg-feature-col" id="rpg-narrator-toggle-wrapper">
                     <label class="rpg-toggle-label" title="Narrator Mode">