feat(CRIT-010): add zone-to-county mapping and county_id to oil_prices

Add ZONE_COUNTY_MAP for all 5 scraped states (42 zone-to-county entries).
Scraper now resolves county_id at startup and assigns it to each record.
Upsert logic deduplicates by (name, state, county_id) to prevent duplicates
when multiple zones map to the same county. Also adds County model for
DB lookups and fixes Rhode Island zone count (4, not 5).

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

models.py

@@ -24,11 +24,20 @@ class OilPrice(Base):
     # when a new record is created and this field is not explicitly set.
 
     company_id = Column(Integer, ForeignKey("company.id"), nullable=True)
+    county_id = Column(Integer, nullable=True)
 
     def __repr__(self):
         return (f"<OilPrice(id={self.id}, state='{self.state}', zone='{self.zone}', "
                 f"name='{self.name}', price={self.price}, date='{self.date}', "
-                f"scraped_at='{self.scrapetimestamp}')>") # Added scraped_at to repr
+                f"county_id={self.county_id}, scraped_at='{self.scrapetimestamp}')>")
+
+# --- County Model (read-only, for lookups) ---
+class County(Base):
+    __tablename__ = "county"
+
+    id = Column(Integer, primary_key=True)
+    name = Column(String(255))
+    state = Column(String(2))
 
 # --- Company Model (remains the same) ---
 class Company(Base):