Expand emoji picker from ~180 to ~940 curated emoji

The old list was a small hand-picked subset that was missing common
ones (party popper, facepalm, shrug, etc.). Reorganized into ten
categories (Smileys, People & Gestures, Hearts, Animals & Nature,
Food & Drink, Travel & Places, Activities & Sports, Objects, Symbols,
Flags) with much broader coverage in each. Widened the picker panel
and bumped the grid to 9 columns to fit the larger set comfortably.

frontend/src/components/EmojiPicker.css

@@ -7,8 +7,8 @@
 .emoji-picker {
   position: absolute;
   z-index: 31;
-  width: 280px;
-  max-height: 320px;
+  width: 320px;
+  max-height: 380px;
   overflow-y: auto;
   background: var(--card-bg);
   border: 1px solid var(--ds-border);
@@ -46,7 +46,7 @@
 
 .emoji-picker-grid {
   display: grid;
-  grid-template-columns: repeat(8, 1fr);
+  grid-template-columns: repeat(9, 1fr);
   gap: 2px;
 }