Refactor localization structure for production notifications in English and German

- Updated the localization files to nest the "overproduction" notification under a "production" key for better organization and clarity.
- Ensured consistency in translation structure across both English and German localization files.

frontend/src/i18n/locales/de/falukant.json

@@ -16,7 +16,9 @@
         },
         "notifications": {
             "notify_election_created": "Es wurde eine neue Wahl ausgeschrieben.",
-            "production.overproduction": "Überproduktion: Deine Produktion liegt {value}% über dem Bedarf."
+            "production": {
+                "overproduction": "Überproduktion: Deine Produktion liegt {value}% über dem Bedarf."
+            }
         },
         "health": {
             "amazing": "Super",

frontend/src/i18n/locales/en/falukant.json

@@ -7,7 +7,9 @@
         },
         "notifications": {
             "notify_election_created": "A new election has been scheduled.",
-            "production.overproduction": "Overproduction: your production is {value}% above demand."
+            "production": {
+                "overproduction": "Overproduction: your production is {value}% above demand."
+            }
         },
         "statusbar": {
             "age": "Age",