Phase 0 Complete: Tasks 0.7-0.20

- 0.7: UI-Design-Richtlinien (docs/ui-design-guidelines.md, 535 lines)
- 0.8: Theme-Customization Backend (4 theme fields, migration 0023)
- 0.9: Theme-Customization Frontend (SettingsTheme.tsx, themeStore.ts, live preview)
- 0.10: RBAC-Audit (4 plugins secured, 53 routes with require_permission)
- 0.11: LiteLLM-Cleanup (llm_client.py migrated from httpx to litellm)
- 0.12: KI-Agent-Framework docs (plugin-development-guide.md, agent_capabilities field)
- 0.13: Heartbeat configurable (ProactiveSettings, migration 0024, frontend UI)
- 0.14: Unified Search Field-Level RBAC (resolve_permissions + filter_fields_by_permission)
- 0.15: Undo/History-System (EntityHistory model, service, routes, migration 0025, HistoryViewer)
- 0.16: Storage Backend (LocalStorage + S3Storage, DMS/attachments/mail updated)
- 0.17: Import/Export unified Contact fields (firstname, surname, email_1, phone_1)
- 0.18: .gitignore & Config-Cleanup (webui→frontend, python-jose removed, .env untracked)
- 0.19: Mail-Salt Security-Fix (per-account random salt, migration 0026)
- 0.20: AGPL replaced (PyMuPDF→pypdf, OnlyOffice→Collabora, LICENSE + THIRD_PARTY_LICENSES.md)

app/schemas/system_settings.py

@@ -24,6 +24,11 @@ class SystemSettingsUpsert(BaseModel):
     invoice_prefix: str = Field("RE-", max_length=20)
     quote_prefix: str = Field("AN-", max_length=20)
     payment_terms_days: int = Field(14, ge=0, le=365)
+    # Theme customization
+    theme_primary_color: str = Field("#2563eb", max_length=20)
+    theme_accent_color: str = Field("#d946ef", max_length=20)
+    theme_font_family: str = Field("Inter", max_length=100)
+    theme_border_radius: str = Field("0.5rem", max_length=20)
 
 
 class SystemSettingsResponse(BaseModel):
@@ -46,5 +51,10 @@ class SystemSettingsResponse(BaseModel):
     invoice_prefix: str = "RE-"
     quote_prefix: str = "AN-"
     payment_terms_days: int = 14
+    # Theme customization
+    theme_primary_color: str = "#2563eb"
+    theme_accent_color: str = "#d946ef"
+    theme_font_family: str = "Inter"
+    theme_border_radius: str = "0.5rem"
     created_at: str | None = None
     updated_at: str | None = None