Migrate user/profile URLs to /u/[handle] and remove legacy scripts

All user and post profile URLs have been updated from /[handle] to /u/[handle] for consistency. Added a redirect page for /posts/[id] to the canonical /u/[handle]/posts/[id] route. Deprecated and removed legacy scripts and documentation related to chat and federation endpoints. Push-based federation endpoints are now disabled in favor of real-time pull-based federation.

src/app/settings/bots/page.tsx

@@ -111,7 +111,7 @@ export default function BotsPage() {
               <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'start', marginBottom: '12px' }}>
                 <div style={{ display: 'flex', gap: '12px', flex: 1, minWidth: 0 }}>
                   <Link 
-                    href={`/${bot.handle}`} 
+                    href={`/u/${bot.handle}`} 
                     onClick={(e) => e.stopPropagation()}
                     className="avatar"
                     style={{ 
@@ -147,7 +147,7 @@ export default function BotsPage() {
                       )}
                     </div>
                     <Link 
-                      href={`/${bot.handle}`} 
+                      href={`/u/${bot.handle}`} 
                       onClick={(e) => e.stopPropagation()}
                       style={{ fontSize: '13px', color: 'var(--foreground-tertiary)' }}
                     >