refactor(price): remove price comparison UI and catalog sync

GoMag vs ROA price comparison generated too many false positives
(kits, volume discounts, special prices). Removes comparison columns,
dots, badges, catalog sync endpoints, and ~950 lines of dead code.
Keeps WRITE path (sync_prices_from_order) for kit pricing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

api/app/main.py

@@ -1,4 +1,3 @@
-import asyncio
 from contextlib import asynccontextmanager
 from datetime import datetime
 from fastapi import FastAPI
@@ -9,7 +8,6 @@ import os
 
 from .config import settings
 from .database import init_oracle, close_oracle, init_sqlite
-from .routers.sync import backfill_price_match
 
 # Configure logging with both stream and file handlers
 _log_level = getattr(logging, settings.LOG_LEVEL.upper(), logging.INFO)
@@ -58,8 +56,6 @@ async def lifespan(app: FastAPI):
     except Exception:
         pass
 
-    asyncio.create_task(backfill_price_match())
-
     logger.info("GoMag Import Manager started")
     yield