Add automatic generation of favourite buttons

favourite buttons are based on how often a good i added to list
finished implementing setting category
made number of days until button an environment variable

rebase on main and fix

ran cargo fmt

srv/Cargo.toml

@@ -9,3 +9,4 @@ serde = { version = "1.0.228", features = ["derive"] }
 serde_json = "1.0.145"
 inkopslista-lib = { path = "../lib" }
 sqlite = "0.37.0"
+clap = { version = "4.6.6", features = ["derive", "env"] }