refactor: unify settings layout, navigation and copy

Consolidate the personal, team and organisation settings surfaces behind a single
system so every page shares one width, one navigation implementation and one copy
standard.

- add shared SettingsNav (aria-current active state, exact matching for the team
  General route, non-interactive section labels) and delete the four divergent nav
  implementations it replaces
- constrain the settings content column to max-w-3xl in all three layouts and strip
  the per-page max-w-2xl/max-w-xl wrappers so forms and tables render identically
- rewrite SettingsHeader subtitles to remove "Here you can" / "On this page" filler,
  normalize title casing and punctuation, and translate the hardcoded team general
  header
- align the billing header with SettingsHeader typography and drop redundant fieldset
  width constraints in the document/email preference forms
- fix the wrong team group success toast, team email meta title, misnamed page
  exports, untranslated Manage label and Create Team casing mismatch
- update manage-organisation e2e assertions for the corrected copy

apps/remix/app/components/forms/document-preferences-form.tsx

@@ -162,7 +162,7 @@ export const DocumentPreferencesForm = ({
   return (
     <Form {...form}>
       <form onSubmit={handleFormSubmit}>
-        <fieldset className="flex h-full max-w-2xl flex-col gap-y-6" disabled={form.formState.isSubmitting}>
+        <fieldset className="flex h-full flex-col gap-y-6" disabled={form.formState.isSubmitting}>
           {!isPersonalLayoutMode && (
             <FormField
               control={form.control}

apps/remix/app/components/forms/email-preferences-form.tsx

@@ -75,7 +75,7 @@ export const EmailPreferencesForm = ({ settings, onFormSubmit, canInherit }: Ema
   return (
     <Form {...form}>
       <form onSubmit={handleFormSubmit}>
-        <fieldset className="flex h-full max-w-2xl flex-col gap-y-6" disabled={form.formState.isSubmitting}>
+        <fieldset className="flex h-full flex-col gap-y-6" disabled={form.formState.isSubmitting}>
           {organisation.organisationClaim.flags.emailDomains && (
             <FormField
               control={form.control}