feat: custom branding (#112)

* add first concept

* remove setup status

* split config page in multiple components

* add custom branding docs

* add test email button

* fix invalid email from header

* add migration

* mount images to host

* update docs

* remove unused endpoint

* run formatter

backend/prisma/schema.prisma

@@ -131,13 +131,15 @@ model ShareSecurity {
 model Config {
   updatedAt DateTime @updatedAt
 
-  key         String  @id
+  name        String
+  category    String
   type        String
   value       String
   description String
-  category    String
   obscured    Boolean @default(false)
   secret      Boolean @default(true)
   locked      Boolean @default(false)
   order       Int
+
+  @@id([name, category])
 }