Add fullscreen firework emoji confetti and fix Linux URL paste.

Sparkle 🎆/🎇 from the jumbo emoji with a lightweight particle fountain that piles on the floor. Prefer text/plain over sticky clipboard images on Linux so address-bar URLs do not also attach a leftover bitmap.

src/app/features/room/emoji-confetti/emojiParticleProfiles.ts

@@ -7,7 +7,8 @@ export type BurstMotionStyle =
   | 'spiral'
   | 'punch'
   | 'scatter'
-  | 'shower';
+  | 'shower'
+  | 'firework';
 
 export type EmojiBurstProfile = {
   style: BurstMotionStyle;
@@ -32,6 +33,8 @@ export type EmojiBurstProfile = {
   angleSpread?: number;
   twinkle?: boolean;
   wobble?: boolean;
+  /** Full-viewport overlay (Box2D pile for fireworks). */
+  fullscreen?: boolean;
 };
 
 const DEFAULT_PROFILE: EmojiBurstProfile = {
@@ -340,6 +343,45 @@ const PROFILE_OVERRIDES: Record<string, Partial<EmojiBurstProfile>> = {
     companions: ['🎉', '🎊', '🎈'],
     companionChance: 0.4,
   },
+  '🎆': {
+    style: 'firework',
+    fullscreen: true,
+    particleCount: 320,
+    gravity: 980,
+    drag: 1,
+    speedMin: 420,
+    speedMax: 980,
+    launchUpMin: 180,
+    launchUpMax: 420,
+    spinMin: -520,
+    spinMax: 520,
+    fontSizeMin: 16,
+    fontSizeMax: 30,
+    heroFontSizeMin: 40,
+    heroFontSizeMax: 52,
+    companions: ['🎇', '✨', '💥', '⭐', '🎉'],
+    companionChance: 0.55,
+  },
+  '🎇': {
+    style: 'firework',
+    fullscreen: true,
+    particleCount: 280,
+    gravity: 960,
+    drag: 1,
+    speedMin: 380,
+    speedMax: 920,
+    launchUpMin: 160,
+    launchUpMax: 400,
+    spinMin: -480,
+    spinMax: 480,
+    fontSizeMin: 14,
+    fontSizeMax: 28,
+    heroFontSizeMin: 36,
+    heroFontSizeMax: 48,
+    companions: ['🎆', '✨', '⭐', '💥'],
+    companionChance: 0.5,
+    twinkle: true,
+  },
   '🐱': {
     style: 'bounce',
     particleCount: 20,
@@ -369,6 +411,10 @@ export function getEmojiBurstProfile(emoji: string): EmojiBurstProfile {
   return { ...DEFAULT_PROFILE, ...override };
 }
 
+export function isFullscreenBurstEmoji(emoji: string): boolean {
+  return getEmojiBurstProfile(emoji).fullscreen === true;
+}
+
 export function pickParticleEmoji(profile: EmojiBurstProfile, primaryEmoji: string): string {
   if (!profile.companions?.length || !profile.companionChance) {
     return primaryEmoji;