Fix TypeError: Remove await from background_tasks.add_task calls

The HybridBackgroundTasks.add_task() method returns None and should not be awaited.
This was causing production errors with 'TypeError: object NoneType can't be used in 'await' expression'.

Fixed in:
- agent_memory_server/api.py (3 locations)
- agent_memory_server/long_term_memory.py (2 locations)

Resolves the 500 Internal Server Error on POST /v1/long-term-memory/

Author: abrookins

agent_memory_server/api.py

@@ -507,7 +507,7 @@ async def put_working_memory(
         updated_memory.memories or updated_memory.messages
     ):
         # Promote structured memories from working memory to long-term storage
-        await background_tasks.add_task(
+        background_tasks.add_task(
             long_term_memory.promote_working_memory_to_long_term,
             session_id=session_id,
             user_id=updated_memory.user_id,
@@ -596,7 +596,7 @@ async def create_long_term_memory(
         # Clear any client-provided persisted_at value
         memory.persisted_at = None
 
-    await background_tasks.add_task(
+    background_tasks.add_task(
         long_term_memory.index_long_term_memories,
         memories=payload.memories,
     )
@@ -732,7 +732,7 @@ def _vals(f):
         ids = [m.id for m in ranked if m.id]
         if ids:
             background_tasks = get_background_tasks()
-            await background_tasks.add_task(long_term_memory.update_last_accessed, ids)
+            background_tasks.add_task(long_term_memory.update_last_accessed, ids)
 
         raw_results.memories = ranked
         return raw_results

agent_memory_server/long_term_memory.py

@@ -842,7 +842,7 @@ async def index_long_term_memories(
 
     # Schedule background tasks for topic/entity extraction
     for memory in processed_memories:
-        await background_tasks.add_task(extract_memory_structure, memory)
+        background_tasks.add_task(extract_memory_structure, memory)
 
     if settings.enable_discrete_memory_extraction:
         needs_extraction = [
@@ -853,7 +853,7 @@ async def index_long_term_memories(
         # Extract discrete memories from the indexed messages and persist
         # them as separate long-term memory records. This process also
         # runs deduplication if requested.
-        await background_tasks.add_task(
+        background_tasks.add_task(
             extract_memories_with_strategy,
             memories=needs_extraction,
             deduplicate=deduplicate,