refactor(memory): remove legacy extraction pipeline and add dialog_at temporal grounding

- Delete ExtractionOrchestrator (~2500 lines) and write_tools legacy path;
  MemoryService/WritePipeline is now the sole write path
- Remove NEW_PIPELINE_ENABLED feature flag from memory_agent_service
- Simplify pilot_run_service to always use PilotWritePipeline
- Add dialog_at field to statement and triplet extraction prompts as the
  primary reference time for resolving relative temporal expressions
- Rewrite relative time phrases (e.g. 昨天, 下周) into concrete dates
  directly in statement_text when stably resolvable from dialog_at
- Rename extracat_Pruning.jinja2 to extracat_pruning.jinja2; expand
  few-shot examples and update memory type enum (drop NULL, add
  agreement/repetition/other)

api/app/core/config.py

@@ -272,12 +272,6 @@ class Settings:
     
     MEMORY_OUTPUT_DIR: str = os.getenv("MEMORY_OUTPUT_DIR", "logs/memory-output")
     MEMORY_CONFIG_DIR: str = os.getenv("MEMORY_CONFIG_DIR", "app/core/memory")
-    # Pilot run pipeline switch:
-    # true  -> use refactored PilotWritePipeline
-    # false -> use legacy ExtractionOrchestrator pipeline
-    PILOT_RUN_USE_REFACTORED_PIPELINE: bool = (
-        os.getenv("PILOT_RUN_USE_REFACTORED_PIPELINE", "true").lower() == "true"
-    )
 
     # Tool Management Configuration
     TOOL_CONFIG_DIR: str = os.getenv("TOOL_CONFIG_DIR", "app/core/tools")