feat: wire contract PDF context and align MechanicAuto with AutoEvaluation

- contract PDF: map report/customer/owner/contract from AutoEvaluationModel
  fields, accept inspection via POST serializer, fetch CBU.uz currency rates
- MechanicAutoEvaluation: add distance_covered, object_owner_residence and
  car_position/body_type/fuel_type/state_car/assessment_task_type FKs; drop
  car_type and single tex_passport_file in favour of multi-file FK model

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

core/apps/documents/services/cbu_rates.py

@@ -0,0 +1,33 @@
+from datetime import date
+
+import requests
+
+CBU_URL = "https://cbu.uz/oz/arkhiv-kursov-valyut/json/{code}/{date}/"
+TIMEOUT_SECONDS = 5
+CURRENCY_CODES = ("USD", "EUR", "RUB")
+
+
+def fetch_rates(target_date):
+    """CBU.uz dan berilgan sanaga oid USD, EUR, RUB kurslarini olish.
+
+    Tarmoq xatosi yoki notogri javob bolsa bosh dict qaytadi.
+    """
+    if target_date is None:
+        target_date = date.today()
+    date_str = target_date.strftime("%Y-%m-%d")
+    rates = {}
+    for code in CURRENCY_CODES:
+        try:
+            resp = requests.get(
+                CBU_URL.format(code=code, date=date_str),
+                timeout=TIMEOUT_SECONDS,
+            )
+            resp.raise_for_status()
+            data = resp.json()
+            if isinstance(data, list) and data:
+                rate_value = data[0].get("Rate")
+                if rate_value:
+                    rates[code] = rate_value
+        except (requests.RequestException, ValueError):
+            continue
+    return rates