feat(validators): add noqa suppression support to security and performance validators

- Add centralized _is_noqa_suppressed() to BaseValidator with normalization
  (accepts both SEC001 and SEC-001 formats for ruff compatibility)
- Wire noqa support into all 21 security and 18 performance check functions
- Add ruff external config for SEC/PERF/MOD/EXC codes in pyproject.toml
- Convert all 280 Python noqa comments to dashless format (ruff-compatible)
- Add site/ to IGNORE_PATTERNS (excludes mkdocs build output)
- Suppress 152 false positive findings (test passwords, seed data, validator
  self-references, Apple Wallet SHA1, etc.)
- Security: 79 errors → 0, 60 warnings → 0
- Performance: 80 warnings → 77 (3 test script suppressions)
- Add proposal doc with noqa inventory and remaining findings recommendations

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

app/modules/billing/exceptions.py

@@ -90,7 +90,7 @@ class SubscriptionNotCancelledException(BusinessLogicException):
         )
 
 
-class SubscriptionAlreadyCancelledException(BusinessLogicException):  # noqa: MOD-025
+class SubscriptionAlreadyCancelledException(BusinessLogicException):  # noqa: MOD025
     """Raised when trying to cancel an already cancelled subscription."""
 
     def __init__(self):
@@ -170,7 +170,7 @@ class StripePriceNotConfiguredException(BusinessLogicException):
         self.tier_code = tier_code
 
 
-class PaymentFailedException(BillingException):  # noqa: MOD-025
+class PaymentFailedException(BillingException):  # noqa: MOD025
     """Raised when a payment fails."""
 
     def __init__(self, message: str, stripe_error: str | None = None):