feat(nav): concept sidebar with folds, collapse rail, and user menu (UI migration PR 2) (#1133)

* feat(nav): concept sidebar with folds, collapse rail, and user menu (UI migration PR 2)

The concept's navigation, exactly, with all current functionality kept:

- Groups restructured per concept: top (Hem, Assistenten), ARBETA
  (Bokforing, Underlag, Transaktioner, Granskning, Kundfakturor,
  Leverantorsfakturor, Loner), ANALYS, DATA (Register fold +
  Importera/exportera), SKATT & BOKSLUT (Moms, Skattekonto, Viktiga
  datum, Bokslut fold). Entity/capability/dimension gating unchanged.
- Register and Bokslut are animated folds (grid-rows 0fr/1fr), children
  text-indented behind a hairline; closed by default, forced open by an
  active child route; state persists per user.
- Sidebar collapses to a 64px icon rail (toggle top of rail); width is
  one inline --nav-w CSS variable on #dash-shell that aside and <main>
  both read, so the panel follows in lockstep. Server-rendered from
  ui_state so first paint is right.
- Sticky bottom user block (avatar, name, active company) opening an
  upward user menu: identity, company-switcher flyout (search + building
  glyphs + roles + check, real switch mechanism via shared
  lib/company/switch-client), Installningar, Medlemmar och roller,
  Abonnemang, Hjalp, support, terracotta logout. Trial touchpoint kept.
- CompanySwitcher removed from desktop top (lives in the user menu now);
  mobile bottom nav + sheet unchanged.
- New migration 20260723120000: user_preferences.ui_state jsonb bag
  (founder-approved) + POST /api/user/ui-state (requireAuth, strict zod,
  merge semantics) with route tests.
- i18n: fold/collapse/menu keys added sv+en; deadlines -> "Viktiga
  datum", year_end -> "Arsbokslut" per concept.

Discord-community row deferred: no invite URL exists in the repo.
Badges stay the current two (Transaktioner, Granskning); an Underlag
count is a follow-up with lib/worklist.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(nav): brand-mark sidebar header + auto-hiding scrollbars

Concept alignment feedback: the sidebar gets a header row (brand mark
left, collapse toggle right) hanging from the same top line as the
panel, instead of a lone right-aligned toggle.

Scrollbars go overlay-style app-wide: transparent at rest, revealed only
while their container scrolls (ScrollbarReveal stamps .is-scrolling via
one capture-phase document listener), fading out after 700ms idle. The
gutter stays reserved so revealing never shifts layout.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(nav): company flyout opens downward + Discord community row

The flyout was bottom-anchored to its row and grew upward over the menu;
founder feedback: top-align with the row and grow downward. Adds the
Discord community row to the user menu (external invite link).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

lib/company/switch-client.ts

@@ -0,0 +1,38 @@
+'use client'
+
+import { switchCompany } from '@/lib/company/actions'
+
+/**
+ * Client-side company switch: persists the new active company via the
+ * server action, notifies sibling tabs, then hard-reloads onto the new
+ * company. Shared by CompanySwitcher (mobile sheet) and the sidebar
+ * user-menu flyout so both use the exact same mechanism.
+ *
+ * Returns an error code instead of navigating when the switch fails.
+ */
+export async function performCompanySwitch(
+  companyId: string,
+): Promise<{ error: string } | void> {
+  const result = await switchCompany(companyId)
+  if (result.error) {
+    return { error: result.error }
+  }
+  // Notify every other open tab of the same user so they hard-reload
+  // onto the new company. BroadcastChannel is best-effort: if the
+  // browser doesn't support it (very old) we still hard-reload
+  // ourselves, and other tabs will self-correct via the visibilitychange
+  // / pageshow listeners in CompanyTabSync on their next focus event.
+  if (typeof BroadcastChannel !== 'undefined') {
+    try {
+      const channel = new BroadcastChannel('gnubok-company-switch')
+      channel.postMessage({ companyId })
+      channel.close()
+    } catch {
+      // Ignore: hard reload still happens below
+    }
+  }
+  // Hard navigation: tears down React state, router cache, in-flight
+  // fetches, blob URLs, etc. This is the whole point: nothing from the
+  // previous company can survive the switch.
+  window.location.assign('/')
+}