feat: add admin settings system and improve customer/pricing endpoints

Add centralized admin settings (company info, social links, quick calls,
sidebar visibility toggles, theme, logo upload) with singleton pattern
and full CRUD API. Add active/dedicated customer count endpoints for
dashboard stats. Fix automatic assignment route to use PUT instead of
GET. Refactor oil price endpoint to use schema serialization with null
safety.

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

app/classes/admin.py

@@ -1,5 +1,6 @@
 from app import db, ma
 from datetime import datetime
+import json
 
 
 class Admin_Company(db.Model):
@@ -30,4 +31,30 @@ class Call(db.Model):
 
     id = db.Column(db.Integer, primary_key=True, index=True)
     current_phone = db.Column(db.String(500))
-    created_at = db.Column(db.DateTime, default=datetime.utcnow)
+    created_at = db.Column(db.DateTime, default=datetime.utcnow)
+
+
+class Admin_Settings(db.Model):
+    __tablename__ = 'admin_settings'
+    __table_args__ = {"schema": "public"}
+
+    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
+    updated_at = db.Column(db.TIMESTAMP(), default=datetime.utcnow, onupdate=datetime.utcnow)
+    logo_base64 = db.Column(db.Text, nullable=True)
+    logo_mime_type = db.Column(db.VARCHAR(50), nullable=True)
+    company_name = db.Column(db.VARCHAR(250), default='Auburn Oil')
+    link_facebook = db.Column(db.VARCHAR(500), nullable=True)
+    link_google = db.Column(db.VARCHAR(500), nullable=True)
+    link_website = db.Column(db.VARCHAR(500), nullable=True)
+    link_google_review = db.Column(db.VARCHAR(500), nullable=True)
+    quick_calls = db.Column(db.Text, nullable=True)
+    show_automatics = db.Column(db.Boolean, default=True)
+    show_stats = db.Column(db.Boolean, default=True)
+    show_service = db.Column(db.Boolean, default=True)
+    show_ticker = db.Column(db.Boolean, default=True)
+    default_theme = db.Column(db.VARCHAR(50), default='ocean')
+
+
+class Admin_Settings_schema(ma.SQLAlchemyAutoSchema):
+    class Meta:
+        model = Admin_Settings