refactor: remove backward compatibility code for pre-launch baseline

Clean up accumulated backward-compat shims, deprecated wrappers, unused
aliases, and legacy code across the codebase. Since the platform is not
live yet, this establishes a clean baseline.

Changes:
- Delete deprecated middleware/context.py (RequestContext, get_request_context)
- Remove unused factory get_store_email_settings_service()
- Remove deprecated pagination_full macro, /admin/platform-homepage route
- Remove ConversationResponse, InvoiceSettings* unprefixed aliases
- Simplify celery_config.py (remove empty LEGACY_TASK_MODULES)
- Standardize billing exceptions: *Error aliases → *Exception names
- Consolidate duplicate TierNotFoundError/FeatureNotFoundError classes
- Remove deprecated is_admin_request() from Store/PlatformContextManager
- Remove is_platform_default field, MediaUploadResponse legacy flat fields
- Remove MediaItemResponse.url alias, update JS to use file_url
- Update all affected tests and documentation

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

app/modules/billing/exceptions.py

@@ -19,24 +19,18 @@ from app.exceptions.base import (
 __all__ = [
     # Base billing exception
     "BillingException",
-    "BillingServiceError",  # Alias for backwards compatibility
     # Subscription exceptions
     "SubscriptionNotFoundException",
     "NoActiveSubscriptionException",
-    "NoActiveSubscriptionError",  # Alias for backwards compatibility
     "SubscriptionNotCancelledException",
-    "SubscriptionNotCancelledError",  # Alias for backwards compatibility
     "SubscriptionAlreadyCancelledException",
     # Tier exceptions
     "TierNotFoundException",
-    "TierNotFoundError",
     "TierLimitExceededException",
     # Payment exceptions
     "PaymentSystemNotConfiguredException",
-    "PaymentSystemNotConfiguredError",  # Alias for backwards compatibility
     "StripeNotConfiguredException",
     "StripePriceNotConfiguredException",
-    "StripePriceNotConfiguredError",  # Alias for backwards compatibility
     "PaymentFailedException",
     # Webhook exceptions
     "InvalidWebhookSignatureException",
@@ -44,7 +38,6 @@ __all__ = [
     "WebhookVerificationException",
     # Feature exceptions
     "FeatureNotFoundException",
-    "FeatureNotFoundError",
     "FeatureNotAvailableException",
     "InvalidFeatureCodesError",
 ]
@@ -62,10 +55,6 @@ class BillingException(BusinessLogicException):
         super().__init__(message=message, error_code=error_code, details=details)
 
 
-# Alias for backwards compatibility with billing_service.py
-BillingServiceError = BillingException
-
-
 # =============================================================================
 # Subscription Exceptions
 # =============================================================================
@@ -92,10 +81,6 @@ class NoActiveSubscriptionException(BusinessLogicException):
         )
 
 
-# Alias for backwards compatibility with billing_service.py
-NoActiveSubscriptionError = NoActiveSubscriptionException
-
-
 class SubscriptionNotCancelledException(BusinessLogicException):
     """Raised when trying to reactivate a subscription that is not cancelled."""
 
@@ -106,10 +91,6 @@ class SubscriptionNotCancelledException(BusinessLogicException):
         )
 
 
-# Alias for backwards compatibility with billing_service.py
-SubscriptionNotCancelledError = SubscriptionNotCancelledException
-
-
 class SubscriptionAlreadyCancelledException(BusinessLogicException):
     """Raised when trying to cancel an already cancelled subscription."""
 
@@ -138,18 +119,6 @@ class TierNotFoundException(ResourceNotFoundException):
         self.tier_code = tier_code
 
 
-class TierNotFoundError(ResourceNotFoundException):
-    """Subscription tier not found (alternate naming)."""
-
-    def __init__(self, tier_code: str):
-        super().__init__(
-            resource_type="SubscriptionTier",
-            identifier=tier_code,
-            message=f"Tier '{tier_code}' not found",
-        )
-        self.tier_code = tier_code
-
-
 class TierLimitExceededException(BillingException):
     """Raised when a tier limit is exceeded."""
 
@@ -180,10 +149,6 @@ class PaymentSystemNotConfiguredException(ServiceUnavailableException):
         super().__init__(message="Payment system not configured")
 
 
-# Alias for backwards compatibility with billing_service.py
-PaymentSystemNotConfiguredError = PaymentSystemNotConfiguredException
-
-
 class StripeNotConfiguredException(BillingException):
     """Raised when Stripe is not configured."""
 
@@ -206,10 +171,6 @@ class StripePriceNotConfiguredException(BusinessLogicException):
         self.tier_code = tier_code
 
 
-# Alias for backwards compatibility with billing_service.py
-StripePriceNotConfiguredError = StripePriceNotConfiguredException
-
-
 class PaymentFailedException(BillingException):
     """Raised when a payment fails."""
 
@@ -277,18 +238,6 @@ class FeatureNotFoundException(ResourceNotFoundException):
         self.feature_code = feature_code
 
 
-class FeatureNotFoundError(ResourceNotFoundException):
-    """Feature not found (alternate naming)."""
-
-    def __init__(self, feature_code: str):
-        super().__init__(
-            resource_type="Feature",
-            identifier=feature_code,
-            message=f"Feature '{feature_code}' not found",
-        )
-        self.feature_code = feature_code
-
-
 class FeatureNotAvailableException(BillingException):
     """Raised when a feature is not available in current tier."""