Add currency settings, Settings service, and dialog to select fiat currency. Add support for non Official currencies like DOGE when using rates.

src/cli/autocomplete/scripts/zsh.zsh

@@ -180,6 +180,17 @@ _{{FUNC_NAME}}_completions() {
       fi
       ;;
 
+    settings)
+      if [[ -z "${subcmd}" ]]; then
+        compadd -- show get set
+      elif [[ "${subcmd}" == "get" || "${subcmd}" == "set" ]]; then
+        local pos=$((CURRENT - subcmd_idx))
+        if [[ $pos -eq 1 ]]; then
+          compadd -- currency default-mnemonic
+        fi
+      fi
+      ;;
+
     receive)
       # receive <template> [output]
       local pos=$((CURRENT - cmd_idx))