feat(profile)!: replace sidebar and add avatar navigation

Rename the global Sidebar route, UI, assets, analytics, and payment return context to Profile. Add accessible message-avatar navigation and preserve the source character across auth and logout flows.

BREAKING CHANGE: /sidebar has been removed; use /profile instead.

src/app/coins-rules/coins-rules-screen.tsx

@@ -118,9 +118,9 @@ export function CoinsRulesScreen({ returnTo }: CoinsRulesScreenProps) {
       <main className={styles.screen}>
         <header className={styles.header}>
           <BackButton
-            href={navigation.sidebarUrl}
+            href={navigation.profileUrl}
             variant="soft"
-            aria-label="Back to sidebar"
+            aria-label="Back to profile"
           />
 
           <div className={styles.hero}>