feat(memory): add WritePipeline and MemoryService facade

Introduce a layered pipeline architecture for the memory write flow:
- WritePipeline: orchestrates preprocess → extract → store → cluster → summarize
  with deadlock retry, resource cleanup, and pilot-run support
- MemoryService: facade that delegates to WritePipeline, placeholder methods
  for read/forget/reflect
- BearLogger: structured step-level logging with perf threshold alerts
- Shadow pipeline integration in MemoryAgentService (env-gated pilot run)

Also includes:
- Fix deprecated SQLAlchemy declarative_base import
- Extend Neo4j Entity fulltext index to cover description and aliases
- Migrate Pydantic schemas to v2 (ConfigDict, field_validator)

api/app/schemas/order_schema.py

@@ -4,7 +4,7 @@ Order Schema
 Defines request and response models for order operations.
 """
 
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, ConfigDict, Field
 from typing import Any, Optional
 
 
@@ -17,8 +17,8 @@ class CreateOrderRequest(BaseModel):
     customer_email: Optional[str] = Field(None, description="Customer email")
     notes: Optional[str] = Field(None, description="Order notes")
     
-    class Config:
-        json_schema_extra = {
+    model_config = ConfigDict(
+        json_schema_extra={
             "example": {
                 "product_id": "PROD-001",
                 "quantity": 2,
@@ -27,6 +27,7 @@ class CreateOrderRequest(BaseModel):
                 "notes": "Please deliver before 5pm"
             }
         }
+    )
 
 
 class OrderResponse(BaseModel):
@@ -40,8 +41,8 @@ class OrderResponse(BaseModel):
     created_at: Optional[str] = Field(None, description="Creation timestamp")
     message: Optional[str] = Field(None, description="Response message")
     
-    class Config:
-        json_schema_extra = {
+    model_config = ConfigDict(
+        json_schema_extra={
             "example": {
                 "order_id": "ORD-20231224-001",
                 "status": "pending",
@@ -52,6 +53,7 @@ class OrderResponse(BaseModel):
                 "message": "Order created successfully"
             }
         }
+    )
 
 
 class ExternalOrderResponse(BaseModel):