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

internal/cache/backends/redis.go

@@ -345,7 +345,7 @@ func (r *RedisBackend) prefixKey(key string) string {
 
 // executeWithRetry executes a Redis operation with exponential backoff retry logic.
 // It checks context cancellation at multiple points to ensure fast abort when the
-// caller's context is cancelled (e.g., due to request timeout).
+// caller's context is canceled (e.g., due to request timeout).
 func (r *RedisBackend) executeWithRetry(ctx context.Context, operation func(*RedisConn) error) error {
 	maxRetries := 3
 	baseDelay := 50 * time.Millisecond // Reduced from 100ms to fail faster
@@ -377,7 +377,7 @@ func (r *RedisBackend) executeWithRetry(ctx context.Context, operation func(*Red
 		err = operation(conn)
 		r.pool.Put(conn)
 
-		// Check context after operation - if cancelled, don't bother retrying
+		// Check context after operation - if canceled, don't bother retrying
 		if ctx.Err() != nil {
 			return ctx.Err()
 		}