refactor(heartbeat): move kb/embeddings reindex messages to log only

KB and embeddings reindex status messages were being sent to Discord
as heartbeat results. These are internal housekeeping — now logged
instead of surfaced to the user.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/heartbeat.py

@@ -293,7 +293,8 @@ def _check_kb_index() -> str | None:
     index_file = PROJECT_ROOT / "memory" / "kb" / "index.json"
     if not index_file.exists():
         _run_reindex()
-        return "KB: index regenerat"
+        log.info("KB: index regenerat")
+        return None
 
     index_mtime = index_file.stat().st_mtime
     kb_dir = PROJECT_ROOT / "memory" / "kb"
@@ -305,7 +306,7 @@ def _check_kb_index() -> str | None:
 
     if newer > 0:
         _run_reindex()
-        return f"KB: {newer} fișiere reindexate"
+        log.info("KB: %d fișiere reindexate", newer)
     return None
 
 
@@ -333,7 +334,7 @@ def _check_embeddings() -> str | None:
         indexed = result.get("indexed", 0)
         if indexed > 0:
             chunks = result.get("chunks", 0)
-            return f"Embeddings: {indexed} fisiere reindexate ({chunks} chunks)"
+            log.info("Embeddings: %d fisiere reindexate (%d chunks)", indexed, chunks)
         return None
     except ConnectionError:
         log.warning("Embeddings check skipped: Ollama unreachable")