Split /settings into 4 sub-pages with a sidebar layout

Stream E from docs/information-architecture.md. The settings page was
a single scrollable list of five concerns; split it into four
deep-linkable sections behind a shared sidebar layout, so each
concern has a stable URL, a focused loader (only fetches what that
section needs), and a meta title that reflects the section.

Sections:
- /settings/profile — display name, bio, profile visibility
- /settings/account — email change + danger-zone account deletion
- /settings/security — passkeys
- /settings/connections — sync providers (Wahoo today)

URL pattern: nested routes under a layout. /settings itself
redirects to /settings/profile so the bare URL still lands somewhere
useful without rendering an empty container.

- apps/journal/app/routes/settings.tsx — converted from a single
  scrollable page to a layout that renders the sidebar nav + Outlet.
- apps/journal/app/routes/settings.{profile,account,security,
  connections,_index}.tsx — new files, each with its own loader and
  meta. _index redirects to /settings/profile.
- apps/journal/app/routes.ts — registers the four children + index
  under the settings layout route.
- packages/i18n/src/locales/{en,de}.ts — new settings.nav.{profile,
  account,security,connections} keys for the sidebar labels.

Specs (profile-settings, account-management, connected-services)
are unchanged — they describe behavior, not URL structure. The
journal-landing spec is also unchanged; the navbar still has a
single "Settings" link.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/i18n/src/locales/de.ts

@@ -324,6 +324,12 @@ export default {
     },
     settings: {
       title: "Einstellungen",
+      nav: {
+        profile: "Profil",
+        account: "Konto",
+        security: "Sicherheit",
+        connections: "Verbindungen",
+      },
       profile: {
         title: "Profil",
         displayName: "Anzeigename",

packages/i18n/src/locales/en.ts

@@ -324,6 +324,12 @@ export default {
     },
     settings: {
       title: "Settings",
+      nav: {
+        profile: "Profile",
+        account: "Account",
+        security: "Security",
+        connections: "Connected services",
+      },
       profile: {
         title: "Profile",
         displayName: "Display Name",