No canonical snake_case/camelCase serialization policy

Docs/Backend-Development.md

@@ -465,18 +465,14 @@ class BansByCountryResponse(BaseModel):
 
 ## 5. Pydantic Models
 
-- Every model inherits from `pydantic.BaseModel`.
-- Use `model_config = ConfigDict(strict=True)` where appropriate.
-- Field names use **snake_case** in Python, export as **camelCase** to the frontend via alias generators if needed.
-- Validate at the boundary — once data enters a Pydantic model it is trusted.
-- Use `Field(...)` with descriptions for every field to keep auto-generated docs useful.
-- Separate **request models**, **response models**, and **domain (internal) models** — do not reuse one model for all three.
+### Base Class
+
+Every model in `app/models/` **must** inherit from `BanGuiBaseModel` (defined in `app/models/response.py`), not from `pydantic.BaseModel` directly.
 
 ```python
-from pydantic import BaseModel, Field
-from datetime import datetime
+from app.models.response import BanGuiBaseModel
 
-class BanResponse(BaseModel):
+class BanResponse(BanGuiBaseModel):
     ip: str = Field(..., description="Banned IP address")
     jail: str = Field(..., description="Jail that issued the ban")
     banned_at: datetime = Field(..., description="UTC timestamp of the ban")
@@ -484,6 +480,24 @@ class BanResponse(BaseModel):
     ban_count: int = Field(..., ge=1, description="Number of times this IP was banned")
 ```
 
+`BanGuiBaseModel` sets `strict=True` and documents the naming policy. Do **not** override `model_config` on individual models unless you have a specific, documented reason.
+
+### API Field Naming Policy — snake_case everywhere
+
+All API field names use **`snake_case`** in Python, in the JSON wire format, and in the corresponding TypeScript interfaces. There is no `alias_generator` that converts to camelCase.
+
+- ✅ Python field: `active_jails` → JSON key: `"active_jails"` → TypeScript property: `active_jails`
+- ❌ Do **not** add a camelCase `alias_generator` to individual models.
+- ❌ Do **not** mix field name conventions within a single API response.
+
+This policy eliminates a whole class of frontend–backend contract bugs. If the naming policy ever needs to change (e.g. to emit camelCase), change `BanGuiBaseModel` once — all models update automatically.
+
+### Other Model Rules
+
+- Validate at the boundary — once data enters a Pydantic model it is trusted.
+- Use `Field(...)` with descriptions for every field to keep auto-generated docs useful.
+- Separate **request models**, **response models**, and **domain (internal) models** — do not reuse one model for all three.
+
 ### Using `Literal` Types for Constrained Strings
 
 When a field should only accept a small set of predefined values, use `Literal` to enforce this at the type level: