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.libra.config.ts

@@ -5,7 +5,7 @@ import { defineConfig, type Plugin } from 'vite'
 import { VitePWA } from 'vite-plugin-pwa'
 import { ViteImageOptimizer } from 'vite-plugin-image-optimizer'
 import { visualizer } from 'rollup-plugin-visualizer'
-import { brand, brandAlias, brandAppLogoAliasEntry, brandAssetsPlugin } from './vite-branding'
+import { brand, brandAlias, brandAppLogoAliasEntry, brandAssetsPlugin, brandHubLogoAliasEntry } from './vite-branding'
 
 /**
  * Plugin to rewrite dev server requests to libra.html
@@ -114,6 +114,7 @@ export default defineConfig(({ mode }) => ({
     // with optional `?url` query) doesn't get shadowed by the bare aliases.
     alias: [
       brandAppLogoAliasEntry('libra'),
+      brandHubLogoAliasEntry(),
       ...Object.entries(brandAlias).map(([find, replacement]) => ({ find, replacement })),
       // ORDER MATTERS — @rollup/plugin-alias is first-match-wins.
       // The more specific @/app.config remap must precede the @ prefix