fix(ai-moderation): implement prompt analysis recommendations

- Expand IMPHNEN domain rule to cover wildcard (*.imphnen.*)
- Trim redundant SARA examples from TEXT_ONLY_MODE (save ~950 tokens)
- Add debugging logs for channel culture injection into prompt
- Sync flag validation set with missing flags: potential_evasion, unclear_context

Co-Authored-By: Claude <noreply@anthropic.com>

services/discord-gateway/src/modules/ai-moderation/llmClient.ts

@@ -298,6 +298,8 @@ const VALID_PRIMARY_AI_FLAGS = new Set([
   "self_promo",
   "conflict_instigation",
   "offensive_username",
+  "potential_evasion",
+  "unclear_context",
 ]);
 
 function normalizeFlag(value: string): string | null {