feat(backend): harden pricing mutation contract and sync backend docs

- add typed response schemas for pricing write endpoints
- add stale draft version guard for pricing mutations
- unify pricing API contract around expected_scheme_version_id
- update API route map
- add smoke regression checklist for backend routes and artifact flows

backend/app/schemas/pricing.py

@@ -1,22 +1,4 @@
-from decimal import Decimal, InvalidOperation
-
-from pydantic import BaseModel, Field, field_validator
-
-
-def _validate_decimal_amount(value: Decimal) -> Decimal:
-    try:
-        normalized = Decimal(value)
-    except (InvalidOperation, TypeError, ValueError) as exc:
-        raise ValueError("Некорректная сумма") from exc
-
-    if not normalized.is_finite():
-        raise ValueError("Некорректная сумма")
-
-    return normalized
-
-
-class DeleteResponse(BaseModel):
-    status: str
+from pydantic import BaseModel, Field
 
 
 class PricingCategoryCreateRequest(BaseModel):
@@ -29,6 +11,22 @@ class PricingCategoryUpdateRequest(BaseModel):
     code: str | None = Field(default=None, max_length=128)
 
 
+class PriceRuleCreateRequest(BaseModel):
+    pricing_category_id: str = Field(..., max_length=32)
+    target_type: str = Field(..., pattern="^(seat|group|sector)$")
+    target_ref: str = Field(..., min_length=1, max_length=128)
+    amount: str = Field(..., min_length=1, max_length=32)
+    currency: str = Field(default="RUB", min_length=3, max_length=8)
+
+
+class PriceRuleUpdateRequest(BaseModel):
+    pricing_category_id: str = Field(..., max_length=32)
+    target_type: str = Field(..., pattern="^(seat|group|sector)$")
+    target_ref: str = Field(..., min_length=1, max_length=128)
+    amount: str = Field(..., min_length=1, max_length=32)
+    currency: str = Field(default="RUB", min_length=3, max_length=8)
+
+
 class PricingCategoryItem(BaseModel):
     pricing_category_id: str
     scheme_id: str
@@ -37,6 +35,22 @@ class PricingCategoryItem(BaseModel):
     created_at: str
 
 
+class PriceRuleItem(BaseModel):
+    price_rule_id: str
+    scheme_id: str
+    pricing_category_id: str | None
+    target_type: str
+    target_ref: str
+    amount: str
+    currency: str
+    created_at: str
+
+
+class PricingBundleResponse(BaseModel):
+    categories: list[PricingCategoryItem]
+    rules: list[PriceRuleItem]
+
+
 class PricingCategoryCreateResponse(BaseModel):
     pricing_category_id: str
     scheme_id: str
@@ -51,50 +65,13 @@ class PricingCategoryUpdateResponse(BaseModel):
     code: str | None
 
 
-class PriceRuleCreateRequest(BaseModel):
-    pricing_category_id: str | None = Field(default=None, max_length=32)
-    target_type: str = Field(..., pattern="^(seat|group|sector)$")
-    target_ref: str = Field(..., min_length=1, max_length=128)
-    amount: Decimal
-    currency: str = Field(default="RUB", min_length=3, max_length=8)
-
-    @field_validator("amount")
-    @classmethod
-    def validate_amount(cls, value: Decimal) -> Decimal:
-        return _validate_decimal_amount(value)
-
-
-class PriceRuleUpdateRequest(BaseModel):
-    pricing_category_id: str | None = Field(default=None, max_length=32)
-    target_type: str = Field(..., pattern="^(seat|group|sector)$")
-    target_ref: str = Field(..., min_length=1, max_length=128)
-    amount: Decimal
-    currency: str = Field(default="RUB", min_length=3, max_length=8)
-
-    @field_validator("amount")
-    @classmethod
-    def validate_amount(cls, value: Decimal) -> Decimal:
-        return _validate_decimal_amount(value)
-
-
-class PriceRuleItem(BaseModel):
-    price_rule_id: str
-    scheme_id: str
-    pricing_category_id: str | None
-    target_type: str
-    target_ref: str
-    amount: Decimal | str
-    currency: str
-    created_at: str
-
-
 class PriceRuleCreateResponse(BaseModel):
     price_rule_id: str
     scheme_id: str
-    pricing_category_id: str | None
+    pricing_category_id: str
     target_type: str
     target_ref: str
-    amount: Decimal
+    amount: str
     currency: str
 
 
@@ -104,10 +81,16 @@ class PriceRuleUpdateResponse(BaseModel):
     pricing_category_id: str | None
     target_type: str
     target_ref: str
-    amount: Decimal
+    amount: str
     currency: str
 
 
+class DeleteResponse(BaseModel):
+    deleted: bool
+    pricing_category_id: str | None = None
+    price_rule_id: str | None = None
+
+
 class EffectiveSeatPriceResponse(BaseModel):
     scheme_id: str
     scheme_version_id: str
@@ -117,15 +100,5 @@ class EffectiveSeatPriceResponse(BaseModel):
     matched_rule_level: str
     matched_target_ref: str
     pricing_category_id: str | None
-    amount: Decimal | str
+    amount: str
     currency: str
-
-
-class SchemePricingResponse(BaseModel):
-    categories: list[PricingCategoryItem]
-    rules: list[PriceRuleItem]
-
-
-class PricingBundleResponse(BaseModel):
-    categories: list[PricingCategoryItem]
-    rules: list[PriceRuleItem]