feat(observability): implement global database error logging, Prometheus error metrics, and max 3-panel Grafana dashboard

services/ai_processor.py

@@ -5,6 +5,7 @@ from db.models import Post, TargetChannel
 from db.repository import Repository
 from core.llm import LLMClient
 from core.metrics import DUPLICATES_DETECTED_TOTAL
+from core.error_logger import log_exception
 
 logger = logging.getLogger(__name__)
 
@@ -57,7 +58,7 @@ class AIProcessor:
             if rewritten:
                 return rewritten.strip()
         except Exception as e:
-            logger.error(f"Failed to rewrite post for target {target.id} ({target.title}): {e}")
+            await log_exception("ai_processor.rewrite", e, {"target_id": target.id, "target_title": target.title})
 
         # Fallback if AI fails: clean basic @mentions and append footer
         fallback = raw_text