Split the general Settings page into Profile, Login and Notifications pages

Problem

User settings are split between one general Settings page and a separate Tokens page. The general Settings page mixes unrelated things (profile, passkeys, password, notifications), which is confusing.

Expected behavior

Replace the general Settings page with focused pages:

• Profile: profile image, display name and other profile details.
• Login: the Passkeys and Password sections, moved from Settings.
• Notifications: browser push notification settings (TRACK-28), moved from Settings.
• Tokens: stays as it is today.

The general Settings page is removed.

Acceptance criteria

• Profile, Login and Notifications each have their own route and page, with the existing sections moved over unchanged (same validation, CSRF, modals from TRACK-41, and success and error states).
• The general Settings page is removed. Its old URL redirects to Profile so bookmarks and links keep working, keeping the query string (see TRACK-57).
• Sidebar navigation shows Profile, Login, Notifications and Tokens as clearly grouped account pages, including in the collapsed sidebar (TRACK-33 and TRACK-40).
• The legal links footer that currently lives on Settings (TRACK-42) gets a new home, such as the footer of the account pages.
• Links elsewhere in the app that point at Settings sections (e.g. "add a passkey") go to the new pages.
• Works in light and dark modes and at the supported breakpoints.
• Tests cover: each page renders its sections, the old Settings URL redirects, and auth is required on every page.

Open question

Web sessions currently sit on the Tokens page (TRACK-44). Should they move to Login, alongside passkeys and password?