feat(core): refactor linters config and improve code quality (#119)

- [x] Reorganize golangci-lint configuration with documented disable reasons
- [x] Simplify errcheck and revive linter rules with targeted exclusions
- [x] Pre-compile regex patterns in input_validation.go for performance
- [x] Fix type assertions in memory_shard.go and resp.go with safety checks
- [x] Replace string comparison with EqualFold for case-insensitive matching
- [x] Fix loop variable captures in jwk.go and logout.go
- [x] Change high goroutine log level from Info to Debug in autocleanup.go
- [x] Replace deprecated "cancelled" spelling with "canceled" throughout
- [x] Add nolint annotations for intentional unused parameters
- [x] Improve comment formatting for deprecated functions
- [x] Fix comment spelling: "marshalling" → "marshaling"
- [x] Refactor provider warnings formatting in internal/providers/warnings.go
- [x] Simplify metrics summary building in internal/recovery/metrics.go
- [x] Pre-allocate slice in error_recovery.go GetDegradedServices
- [x] Refactor context cancellation checks in redis.go

cache_manager.go

@@ -20,8 +20,9 @@ var (
 	cacheManagerInitOnce       sync.Once
 )
 
-// GetGlobalCacheManager returns a singleton CacheManager instance
-// Deprecated: Use GetGlobalCacheManagerWithConfig instead
+// GetGlobalCacheManager returns a singleton CacheManager instance.
+//
+// Deprecated: Use GetGlobalCacheManagerWithConfig instead.
 func GetGlobalCacheManager(wg *sync.WaitGroup) *CacheManager {
 	return GetGlobalCacheManagerWithConfig(wg, nil)
 }