refactor: store llm prompts as constants for easy access

Author: CoderUni

lib/constants/constants.dart

@@ -1,4 +1,5 @@
 export 'key_name.dart';
 export 'link.dart';
 export 'llm_models.dart';
+export 'llm_prompts.dart';
 export 'padding.dart';

lib/constants/llm_prompts.dart

@@ -0,0 +1,10 @@
+abstract class LLMPromptConstants {
+  const LLMPromptConstants();
+
+  static const String wordOfTheDayPrompt =
+      'Use millisecond timestamp as nonce. Return raw '
+      'JSON:{"word":...,"pinyin":...,"definitions":[...],'
+      '"exampleSentences":[{"sentence":...,"pinyin":...,'
+      '"translation":...}]}'
+      'Pick a new advanced but common Chinese word each run';
+}

lib/presentation/home/repositories/word_of_the_day_repository.dart

@@ -36,11 +36,7 @@ final class WordOfTheDayRepository {
         DeepSeekUserMessage(
           // TODO: Feed with stuff from user's translation or dictionary
           // history
-          uContent: 'Use millisecond timestamp as nonce. Return raw '
-              'JSON:{"word":...,"pinyin":...,"definitions":[...],'
-              '"exampleSentences":[{"sentence":...,"pinyin":...,'
-              '"translation":...}]}'
-              'Pick a new advanced but common Chinese word each run',
+          uContent: LLMPromptConstants.wordOfTheDayPrompt,
         ),
       ],
       responseFormat: DeepSeekResponseFormat.string,