feat(factor): te_thailand rate/credit/retail/property/confidence + thai_trade external sector; fix sign inversion on bearish factors

- add te_thailand collector (TradingEconomics) -> 8 factors: interest rate,
  business loan growth, consumer credit, household debt/GDP, retail sales YoY,
  consumer confidence, residential property prices, business confidence;
  feed banks/retail/consumer_staples/nonbank_finance/property/telecom/healthcare
- add thai_trade collector (TradingEconomics external sector) -> exports/
  imports/current-account factors (concurrent in-tree work, verified green)
- fix sign inversion: theme weights were negative on sign:-1 factors (NPL,
  inflation, unemployment) so higher NPL/inflation RAISED scores; direction now
  lives only in factor sign, theme weights positive (regression-locked)
- tests: te_thailand parse+direction, value-key resolution contract, dashboard
  8-sources, scheduler vintage counts; suite 362 OK

backend/app/scheduler.py

@@ -39,6 +39,8 @@ _REFRESH_JOBS: List[dict] = [
     {"key": "energy_thai", "label": "โรงกลั่น TOP", "module": "energy_thai", "fn": "fetch_energy_thai", "fetch_module": "energy_thai", "frequency": "quarterly"},
     {"key": "macro_thai", "label": "ภาพรวมประเทศไทย (BOT)", "module": "macro_thai", "fn": "fetch_macro_thai", "fetch_module": "macro_thai", "frequency": "monthly"},
     {"key": "bank_npl", "label": "NPL ภาคการเงิน (BOT)", "module": "bank_npl", "fn": "fetch_bank_npl", "fetch_module": "bank_npl", "frequency": "quarterly"},
+    {"key": "thai_trade", "label": "ดุลการค้า/ส่งออก (TradingEconomics)", "module": "thai_trade", "fn": "fetch_thai_trade", "fetch_module": "thai_trade", "frequency": "monthly"},
+    {"key": "te_thailand", "label": "อัตราดอกเบี้ย/สินเชื่อ/ค้าปลีก/เชื่อมั่น (TE)", "module": "te_thailand", "fn": "fetch_te_thailand", "fetch_module": "te_thailand", "frequency": "monthly"},
 ]
 
 # Frequencies -> minimum seconds between successful refreshes of a job.