Standardize API response envelope shapes across all endpoints

This commit standardizes how API responses are wrapped, solving issue #24.

Problem:
- Inconsistent response envelopes (jails vs items vs bans vs no wrapper)
- Frontend required multiple field name variants
- Integration bugs from branching logic
- No clear pattern for different response types

Solution:
- Created response.py with base classes: PaginatedListResponse,
  CollectionResponse, CommandResponse
- Standardized all list/collection responses to use 'items' field
- Domain-specific field names for detail and aggregation responses
- Updated all backends routers and mappers
- Updated frontend types and hooks to match

Changes:
Backend:
- backend/app/models/response.py (new): Base response models
- backend/app/models/ban.py: Updated responses to inherit from bases
- backend/app/models/jail.py: Updated JailListResponse, JailCommandResponse
- backend/app/models/config.py: Updated collection responses
- backend/app/services/jail_service.py: Updated return statements
- backend/app/mappers/ban_mappers.py: Updated 'bans' to 'items'
- backend/tests/test_mappers/test_ban_mappers.py: Updated tests

Frontend:
- frontend/src/types/jail.ts: Updated response interfaces
- frontend/src/types/config.ts: Updated response interfaces
- frontend/src/hooks/useActiveBans.ts: Updated selector
- frontend/src/hooks/useJailList.ts: Updated selector
- frontend/src/hooks/useJailConfigs.ts: Updated selector
- frontend/src/hooks/useConfigActiveStatus.ts: Updated field access
- frontend/src/hooks/useJailAdmin.ts: Updated field access

Documentation:
- Docs/Backend-Development.md: Added § 4.1 API Response Envelope Policy

The policy defines:
1. Paginated lists use PaginatedListResponse (items, total, page, page_size)
2. Non-paginated collections use CollectionResponse (items, total)
3. Detail responses use entity-specific field names (jail, status, settings)
4. Command responses use CommandResponse (message, success, optional target)
5. Aggregations use domain-specific fields (jails, countries, buckets, bans)

All responses now follow one of these patterns, reducing frontend complexity.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/app/models/config.py

@@ -10,6 +10,7 @@ from typing import Literal
 from pydantic import BaseModel, ConfigDict, Field, field_validator
 
 from app.config import get_settings
+from app.models.response import CollectionResponse
 from app.utils.path_utils import validate_log_path
 
 DNSMode = Literal["yes", "warn", "no", "raw"]
@@ -109,13 +110,13 @@ class JailConfigResponse(BaseModel):
     jail: JailConfig
 
 
-class JailConfigListResponse(BaseModel):
-    """Response for ``GET /api/config/jails``."""
+class JailConfigListResponse(CollectionResponse[JailConfig]):
+    """Response for ``GET /api/config/jails``.
 
-    model_config = ConfigDict(strict=True)
+    Returns a non-paginated collection of jail configurations.
+    """
 
-    jails: list[JailConfig] = Field(default_factory=list)
-    total: int = Field(..., ge=0)
+    pass
 
 
 class JailConfigUpdate(BaseModel):
@@ -920,13 +921,13 @@ class InactiveJail(BaseModel):
     )
 
 
-class InactiveJailListResponse(BaseModel):
-    """Response for ``GET /api/config/jails/inactive``."""
+class InactiveJailListResponse(CollectionResponse[InactiveJail]):
+    """Response for ``GET /api/config/jails/inactive``.
 
-    model_config = ConfigDict(strict=True)
+    Returns a non-paginated collection of inactive jail configurations.
+    """
 
-    jails: list[InactiveJail] = Field(default_factory=list)
-    total: int = Field(..., ge=0)
+    pass
 
 
 class ActivateJailRequest(BaseModel):