feat: improve UI for timespan inputs on admin page (#726)

* Define Timestamp type

* Implement Timestamp utils

* Implement Timespan input

* Use timestamp input on config page

* Add timespan type to config services

* Refactor maxExpiration to use timespan type across services and components

* Update sessionDuration to use timespan type in config and adjust token expiration logic

* Update localized strings

backend/prisma/seed/config.seed.ts

@@ -30,8 +30,8 @@ const configVariables: ConfigVariables = {
       secret: false,
     },
     sessionDuration: {
-      type: "number",
-      defaultValue: "2160",
+      type: "timespan",
+      defaultValue: "3 months",
       secret: false,
     },
   },
@@ -47,8 +47,8 @@ const configVariables: ConfigVariables = {
       secret: false,
     },
     maxExpiration: {
-      type: "number",
-      defaultValue: "0",
+      type: "timespan",
+      defaultValue: "0 days",
       secret: false,
     },
     shareIdLength: {