Add seasonal effects for Pi Day, Pride, Rain, and Storm; enhance existing styles

- Introduced new CSS and JS files for Pi Day, Pride, Rain, and Storm effects.
- Updated existing seasonal styles (e.g., Halloween, Hearts, Resurrection) to improve performance with 'contain: layout paint'.
- Enhanced animations for seasonal effects, including adjustments to keyframes and element creation logic.
- Added configuration options for new effects in the main seasonals.js file.
- Updated test-site.html to include new seasonal options in the dropdown.

Jellyfin.Plugin.Seasonals/Web/test-site.html

@@ -249,6 +249,12 @@
             <option value="summer">Summer (Bubbles)</option>
             <option value="carnival">Carnival (Confetti)</option>
             <option value="cherryblossom">Cherryblossom</option>
+            <option value="earthday">Earth Day</option>
+            <option value="eurovision">Eurovision</option>
+            <option value="piday">Pi-Day</option>
+            <option value="pride">Pride</option>
+            <option value="rain">Rain</option>
+            <option value="storm">Storm (Epilepsy Warning!)</option>
             <option value="custom">⚙ Custom (Local Files)</option>
         </select>
 
@@ -335,6 +341,12 @@
             summer:       { css: 'summer.css',        js: 'summer.js',       container: 'summer-container' },
             carnival:     { css: 'carnival.css',      js: 'carnival.js',     container: 'carnival-container' },
             cherryblossom:     { css: 'cherryblossom.css',      js: 'cherryblossom.js',     container: 'cherryblossom-container' },
+            earthday:     { css: 'earthday.css',      js: 'earthday.js',     container: 'earthday-container' },
+            eurovision:   { css: 'eurovision.css',    js: 'eurovision.js',   container: 'eurovision-container' },
+            piday:        { css: 'piday.css',         js: 'piday.js',        container: 'piday-container' },
+            pride:        { css: 'pride.css',         js: 'pride.js',        container: 'pride-container' },
+            rain:         { css: 'rain.css',          js: 'rain.js',         container: 'rain-container' },
+            storm:        { css: 'storm.css',         js: 'storm.js',        container: 'storm-container' },
         };
 
         const select = document.getElementById('theme-select');
@@ -362,7 +374,9 @@
                 '.christmas-container', '.santa-container', '.autumn-container',
                 '.christmas-container', '.santa-container', '.autumn-container',
                 '.easter-container', '.resurrection-container', '.spring-container',
-                '.summer-container', '.carnival-container'
+                '.summer-container', '.carnival-container', '.cherryblossom-container',
+                '.earthday-container', '.eurovision-container', '.piday-container',
+                '.pride-container', '.rain-container', '.storm-container'
             ];
             knownContainers.forEach(sel => {
                 document.querySelectorAll(sel).forEach(el => {