Implement leveling rewards feature with UI and backend support

- Added functionality to manage role rewards based on user levels in the leveling system.
- Updated the LevelingForm component to include fields for defining rewards, including validation for unique levels.
- Enhanced backend logic to handle reward data storage and retrieval, ensuring proper integration with the existing leveling configuration.
- Introduced localization keys for rewards in both English and German, improving user experience.
- Updated dashboard search index to include rewards settings for easier access.

apps/webui/src/messages/en.json

@@ -522,7 +522,10 @@
       "errors": {
         "multiplierMissingId": "Every multiplier needs a role or channel.",
         "multiplierInvalid": "Multipliers must be a positive number.",
-        "multiplierDuplicate": "Each role or channel may only appear once."
+        "multiplierDuplicate": "Each role or channel may only appear once.",
+        "rewardMissingRole": "Every reward needs a role.",
+        "rewardInvalidLevel": "Level must be a whole number of at least 1.",
+        "rewardDuplicateLevel": "Each level may only have one reward."
       },
       "levelUpTitle": "Level-up message",
       "levelUpMode": "Mode",
@@ -533,7 +536,13 @@
       },
       "levelUpChannelId": "Level-up channel",
       "levelUpMessage": "Message content",
+      "rewardsTitle": "Role rewards",
+      "rewardsDescription": "Choose which role is granted at which level.",
+      "rewardLevel": "Level",
+      "rewardRole": "Role",
+      "addReward": "Add reward",
       "stackRewards": "Stack role rewards",
+      "stackRewardsHint": "On = keep all unlocked reward roles. Off = only the role for the current level.",
       "rankCardTitle": "Rank card",
       "cardAccentColor": "Accent color",
       "cardBackgroundColor": "Background color"