feat: expand tax settings form, refactor settings save flow, and update docs (#159)

Expand the tax settings page with F-skatt, VAT registration, fiscal year start month, and salary payment toggles. Refactor SettingsFormWrapper to support onSuccess callbacks so local state only updates after server confirmation. Fix logo upload to use service client for storage RLS bypass. Allow empty email in settings schema. Update CLAUDE.md with comprehensive multi-tenant, auth, and engine documentation. Remove unused langchain skills.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

components/settings/SettingsFormWrapper.tsx

@@ -5,9 +5,13 @@ import { Button } from '@/components/ui/button'
 import { Loader2, Check } from 'lucide-react'
 import { useToast } from '@/components/ui/use-toast'
 
+type SaveResult =
+  | Record<string, unknown>
+  | { updates: Record<string, unknown>; onSuccess?: (data: Record<string, unknown>) => void }
+
 interface SettingsFormWrapperProps {
   children: React.ReactNode
-  onSave?: (formData: FormData) => Record<string, unknown>
+  onSave?: (formData: FormData) => SaveResult
   className?: string
 }
 
@@ -28,7 +32,12 @@ export function SettingsFormWrapper({ children, onSave, className }: SettingsFor
     if (!onSave) return
 
     const formData = new FormData(e.currentTarget)
-    const updates = onSave(formData)
+    const saveResult = onSave(formData)
+
+    // Support both plain object and { updates, onSuccess } return types
+    const isStructured = saveResult && 'updates' in saveResult && typeof saveResult.updates === 'object'
+    const updates = isStructured ? saveResult.updates : saveResult
+    const onSuccess = isStructured ? (saveResult as { onSuccess?: (data: Record<string, unknown>) => void }).onSuccess : undefined
 
     if (!updates || Object.keys(updates).length === 0) return
 
@@ -48,6 +57,7 @@ export function SettingsFormWrapper({ children, onSave, className }: SettingsFor
         throw new Error(result.error || 'Kunde inte spara inställningar')
       }
 
+      onSuccess?.(result.data ?? updates)
       setSaved(true)
       timerRef.current = setTimeout(() => setSaved(false), 2000)
     } catch (error) {