feat(admin): separate platform CRUD from CMS, add entity selector macro

- Move platforms menu from CMS to Platform Admin section with create/edit
- Add platform create page, API endpoint, and service method
- Remove CMS-specific content from platform list and detail pages
- Create shared entity_selector + entity_selected_badge Jinja macros
- Create entity-selector.js generalizing store-selector.js for any entity
- Add Tom Select merchant filter to stores page with localStorage persistence
- Migrate store-products page to use shared macros (remove 53 lines of duped CSS)
- Fix broken icons: puzzle→puzzle-piece, building-storefront→store, language→translate, server→cube

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

app/modules/tenancy/routes/api/admin_platforms.py

@@ -91,6 +91,21 @@ class PlatformUpdateRequest(BaseModel):
     settings: dict[str, Any] | None = None
 
 
+class PlatformCreateRequest(BaseModel):
+    """Request schema for creating a platform."""
+
+    code: str = Field(..., min_length=2, max_length=50, pattern=r"^[a-z][a-z0-9_-]*$")
+    name: str = Field(..., min_length=1, max_length=100)
+    description: str | None = None
+    description_translations: dict[str, str] | None = None
+    domain: str | None = None
+    path_prefix: str | None = None
+    default_language: str = "fr"
+    supported_languages: list[str] = Field(default_factory=lambda: ["fr", "de", "en", "lb"])
+    is_active: bool = True
+    is_public: bool = True
+
+
 class PlatformStatsResponse(BaseModel):
     """Platform statistics response."""
 
@@ -162,6 +177,26 @@ async def list_platforms(
     return PlatformListResponse(platforms=result, total=len(result))
 
 
+@admin_platforms_router.post("", response_model=PlatformResponse, status_code=201)
+async def create_platform(
+    create_data: PlatformCreateRequest,
+    db: Session = Depends(get_db),
+    current_user: UserContext = Depends(get_current_admin_from_cookie_or_header),
+):
+    """
+    Create a new platform.
+
+    Creates a new platform with the provided configuration.
+    """
+    data = create_data.model_dump()
+    platform = platform_service.create_platform(db, data)
+    db.commit()
+    db.refresh(platform)
+
+    logger.info(f"[PLATFORMS] Created platform: {platform.code}")
+    return _build_platform_response(db, platform)
+
+
 @admin_platforms_router.get("/{code}", response_model=PlatformResponse)
 async def get_platform(
     code: str = Path(..., description="Platform code (oms, loyalty, etc.)"),