fix: reduce excessive log volume by demoting per-request noise to DEBUG (#613)

Demote high-frequency per-request/per-item logs from INFO to DEBUG:
- 🔇 Client routing decisions (async_client.py) — logged every MCP tool call
- 🔇 DB migration checks (db.py) — logged every ASGI client creation
- 🔇 Vector table ensure/ready (sqlite + postgres search repos) — logged every search
- 🔇 Per-entity search index start/complete (search_service.py) — logged every file sync
- 🔇 Incremental scan details + per-file permalink updates (sync_service.py)
- 🔇 MCP search tool params and no-results (search.py)
- 📉 Log retention: "10 days" → 5 files (~50MB cap)

API v2 request/response logs remain at INFO for observability.

Closes #613

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: phernandez <paul@basicmachines.co>

src/basic_memory/sync/sync_service.py

@@ -437,13 +437,13 @@ class SyncService:
         elif project.last_scan_timestamp is not None:
             # Incremental scan: only files modified since last scan
             scan_type = "incremental"
-            logger.info(
+            logger.debug(
                 f"Running incremental scan for files modified since {project.last_scan_timestamp}"
             )
             file_paths_to_scan = await self._scan_directory_modified_since(
                 directory, project.last_scan_timestamp
             )
-            logger.info(
+            logger.debug(
                 f"Incremental scan found {len(file_paths_to_scan)} potentially changed files"
             )
 
@@ -705,7 +705,7 @@ class SyncService:
 
             # If permalink changed, update the file
             if permalink != entity_markdown.frontmatter.permalink:
-                logger.info(
+                logger.debug(
                     f"Updating permalink for path: {path}, old_permalink: {entity_markdown.frontmatter.permalink}, new_permalink: {permalink}"
                 )