feat: Phase 7 Aether Drift — typography, spacing & detail alignment

Align all component typography to the design prototype's exact measurements:
- Message author: 16px bold → 15px semibold
- Message text: 16px → 15px, line-height 1.5
- Timestamps: 12px → 11px
- Category headers: 12px bold → 11px medium, #484854 color
- Member/activity names: 15px → 13.5px with tighter line-height
- Member activity text: 12px → 11px
- Section headers: 12px → 10.5px
- Channel header names: 15px with -0.02em tracking
- Channel topic: 12px → 13px
- Header padding: 16px → 20px
- User area avatar: 32px → 34px

packages/web/src/components/layout/ChannelSidebar.tsx

@@ -281,7 +281,7 @@ export function ChannelSidebar() {
           onClick={() => openModal('serverSettings')}
           className="flex-1 h-full px-4 flex items-center justify-between hover:bg-interactive-hover transition-colors min-w-0"
         >
-          <span className="font-bold text-[16px] text-txt-primary truncate leading-tight">{server.name}</span>
+          <span className="font-bold text-[15px] tracking-[-0.02em] text-txt-primary truncate leading-tight">{server.name}</span>
           <svg width="18" height="18" viewBox="0 0 18 18" fill="currentColor" className="text-txt-tertiary flex-shrink-0">
             <path d="M5.293 7.293a1 1 0 011.414 0L9 9.586l2.293-2.293a1 1 0 111.414 1.414l-3 3a1 1 0 01-1.414 0l-3-3a1 1 0 010-1.414z" />
           </svg>
@@ -306,7 +306,7 @@ export function ChannelSidebar() {
               <svg width="12" height="12" viewBox="0 0 24 24" fill="currentColor" className="opacity-70">
                 <path d="M16.59 8.59L12 13.17 7.41 8.59 6 10l6 6 6-6z" />
               </svg>
-              <span className="text-[12px] font-bold uppercase tracking-wider">Text Channels</span>
+              <span className="text-[11px] font-medium uppercase tracking-[0.06em]" style={{ color: '#484854' }}>Text Channels</span>
             </div>
             {canManageChannels && (
               <button
@@ -344,7 +344,7 @@ export function ChannelSidebar() {
                   <svg width="20" height="20" viewBox="0 0 24 24" fill="currentColor" className="flex-shrink-0 opacity-60">
                     <path d="M5.88657 21C5.57547 21 5.3399 20.7189 5.39427 20.4126L6.00001 17H2.59511C2.28449 17 2.04905 16.7198 2.10259 16.4138L2.27759 15.4138C2.31946 15.1746 2.52722 15 2.77011 15H6.35001L7.41001 9H4.00511C3.69449 9 3.45905 8.71977 3.51259 8.41381L3.68759 7.41381C3.72946 7.17456 3.93722 7 4.18011 7H7.76001L8.39677 3.41262C8.43914 3.17391 8.64664 3 8.88907 3H9.87344C10.1845 3 10.4201 3.28107 10.3657 3.58738L9.76001 7H15.76L16.3968 3.41262C16.4391 3.17391 16.6466 3 16.8891 3H17.8734C18.1845 3 18.4201 3.28107 18.3657 3.58738L17.76 7H21.1649C21.4755 7 21.711 7.28023 21.6574 7.58619L21.4824 8.58619C21.4406 8.82544 21.2328 9 20.9899 9H17.41L16.35 15H19.7549C20.0655 15 20.301 15.2802 20.2474 15.5862L20.0724 16.5862C20.0306 16.8254 19.8228 17 19.5799 17H16L15.3632 20.5874C15.3209 20.8261 15.1134 21 14.8709 21H13.8866C13.5755 21 13.3399 20.7189 13.3943 20.4126L14 17H8.00001L7.36325 20.5874C7.32088 20.8261 7.11337 21 6.87094 21H5.88657ZM9.41001 9L8.35001 15H14.35L15.41 9H9.41001Z" />
                   </svg>
-                  <span className={`truncate text-[15px] flex-1 text-left ${isUnread ? 'font-bold' : 'font-medium'}`}>{channel.name}</span>
+                  <span className={`truncate text-[15px] flex-1 text-left ${isUnread ? 'font-semibold' : 'font-medium'}`}>{channel.name}</span>
                   {canManageChannels && (
                     <svg
                       width="16"
@@ -373,7 +373,7 @@ export function ChannelSidebar() {
               <svg width="12" height="12" viewBox="0 0 24 24" fill="currentColor" className="opacity-70">
                 <path d="M16.59 8.59L12 13.17 7.41 8.59 6 10l6 6 6-6z" />
               </svg>
-              <span className="text-[12px] font-bold uppercase tracking-wider">Voice Channels</span>
+              <span className="text-[11px] font-medium uppercase tracking-[0.06em]" style={{ color: '#484854' }}>Voice Channels</span>
             </div>
             {canManageChannels && (
               <button
@@ -724,9 +724,9 @@ function UserAreaPanel({
       <div className="h-[52px] px-2 flex items-center select-none">
         {/* Avatar + name */}
         <div className="p-1 hover:bg-interactive-hover rounded-[4px] flex items-center gap-2 flex-1 min-w-0 cursor-pointer transition-colors group">
-          <Avatar src={user.avatar} name={user.displayName ?? user.username} size={32} status={user.status as any} user={user} />
+          <Avatar src={user.avatar} name={user.displayName ?? user.username} size={34} status={user.status as any} user={user} />
           <div className="flex-1 min-w-0">
-            <div className="text-[13px] font-semibold text-txt-primary truncate leading-tight">{user.displayName ?? user.username}</div>
+            <div className="text-[13.5px] font-semibold text-txt-primary truncate leading-tight">{user.displayName ?? user.username}</div>
             <div className="text-[11px] text-txt-tertiary truncate leading-tight group-hover:text-txt-secondary">@{user.username}</div>
           </div>
         </div>