feat: rewrite K-factor engine with history tracking and outlier detection

Replace simple exponential smoothing with a rolling-average K-factor
system backed by a new auto_kfactor_history table. Budget fills are
detected and excluded from calculations, outliers beyond 2-sigma are
flagged, and confidence scores track data quality per customer.
Adds backfill endpoint, auto-create for missing estimation records,
and manual house_factor PUT endpoints for both auto and regular customers.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/models/auto.py

@@ -1,6 +1,6 @@
 from sqlalchemy import (Column, Integer,
-        DECIMAL, TEXT,
-        VARCHAR, DATE, INTEGER)
+        DECIMAL, TEXT, Boolean,
+        VARCHAR, DATE, INTEGER, Index)
 from datetime import datetime
 from database import  Base
 
@@ -57,11 +57,12 @@ class Auto_Delivery(Base):
     estimated_gallons_left_prev_day = Column(DECIMAL(6, 2))
     tank_height = Column(VARCHAR(25))
     tank_size = Column(VARCHAR(25))
-    house_factor = Column(DECIMAL(5, 2))
+    house_factor = Column(DECIMAL(7, 4))
     auto_status =  Column(INTEGER())
     open_ticket_id = Column(Integer, nullable=True)
     hot_water_summer = Column(INTEGER())
-
+    confidence_score = Column(INTEGER(), default=20)
+    k_factor_source = Column(VARCHAR(20), default='default')
 
 
 
@@ -92,3 +93,24 @@ class Tickets_Auto_Delivery(Base):
     payment_type = Column(Integer, nullable=True)
     payment_card_id = Column(Integer, nullable=True)
     payment_status = Column(Integer, nullable=True)
+    is_budget_fill = Column(Boolean, default=False)
+
+
+class KFactorHistory(Base):
+    __tablename__ = 'auto_kfactor_history'
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    customer_id = Column(INTEGER(), nullable=False, index=True)
+    ticket_id = Column(Integer, nullable=True)
+    fill_date = Column(DATE())
+    gallons_delivered = Column(DECIMAL(6, 2))
+    total_hdd = Column(DECIMAL(8, 2))
+    days_in_period = Column(Integer)
+    k_factor = Column(DECIMAL(7, 4))
+    is_budget_fill = Column(Boolean, default=False)
+    is_outlier = Column(Boolean, default=False)
+    created_at = Column(DATE())
+
+    __table_args__ = (
+        Index('ix_auto_kfactor_history_customer_fill', 'customer_id', fill_date.desc()),
+    )