feat(layout): re-enable "Back to hub" with a sticky sheet footer

Reverses the events-only hide (c037d45) now that the link has a real
home. Three parts:

- Add a @brand-hub-logo alias (brandHubLogoAliasEntry) resolving to the
  brand's primary/global logo — the HUB's logo, never the per-standalone
  @brand-app-logo. Wired into all 9 app vite configs since the shared
  ProfileSheetContent renders it.
- Restructure the profile sheet into a fixed-height flex column: a
  flex-1 min-h-0 overflow-y-auto scroll region over a shrink-0 footer,
  so "Back to hub" + the log-in/out bar stay pinned to the bottom while
  the identity/preferences area scrolls.
- Move the edit-profile Dialog out of the flex root (it portals to body,
  so it's not part of the sheet flow).

Logo bumped to w-8 h-8, centered, with tightened footer padding.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

vite-branding.ts

@@ -115,6 +115,22 @@ export function brandAppLogoAliasEntry(app?: string) {
   } as const
 }
 
+/**
+ * Hub-logo alias entry. Resolves `@brand-hub-logo` to the brand's
+ * primary/global logo (the hub's logo), independent of which standalone
+ * is building. Unlike {@link brandAppLogoAliasEntry}, this never takes an
+ * `app` argument — the "Back to hub" link in every standalone must point
+ * at the HUB's logo, not the current standalone's own logo. Wire it into
+ * every vite.<app>.config.ts that builds ProfileSheetContent.vue.
+ */
+export function brandHubLogoAliasEntry() {
+  const resolved = resolveAppLogo()
+  return {
+    find: /^@brand-hub-logo(\?.*)?$/,
+    replacement: `${resolved}$1`,
+  } as const
+}
+
 /**
  * Optional brand banner — a wide lockup (logo + wordmark in one image)
  * that replaces the logo + app-name pair in a standalone's header.