fix(settings): always open on Account section, drop cross-session state

[h4yfans]

What

Settings modal now always opens on the Account section, and the active section no longer survives close/reopen or app restart.

Why

The active settings section was persisted to localStorage under memry_settings_section, so if a user left the modal on e.g. Editor, that's where the modal reopened next time — even after relaunching the app. The requirement is that Account is the default entry point every time settings opens.

How

• Lifted activeSection state from <SettingsPage> into SettingsModalProvider so the context owns it.
• open(section?) now resets activeSection to section ?? 'account' on every invocation. Existing deep-link callers (openSettings('ai'), openSettings('journal'), openSettings('account')) keep working because an explicit section still wins.
• Deleted the localStorage read/write in settings.tsx and the synthetic StorageEvent dispatch in the context — both were only needed to sync state between the two components when the child owned it.
• Exported a SettingsSection union type from the context so the child no longer needs its own copy.

Radix <Dialog> already unmounts <SettingsPage> on close, so context state + fresh open() call gives us the "reset to Account" behavior cleanly, without needing a useEffect to reset on close.

Type

• fix — bug fix

Test plan

• Manual testing: opened Settings, switched to Editor, closed, reopened → lands on Account. Relaunched app → still lands on Account. Triggered openSettings('ai') from the capture input (AI-not-configured flow) → lands on AI Assistant as before.
• pnpm typecheck:web clean.
• Unit tests — not added; behavior is a single state source in the context and exercised via manual QA.

Checklist

• Self-reviewed the diff
• No hardcoded secrets or credentials
• Files stay under ~500 LOC
• Follows immutable data patterns