feat(rate-limiting): Implement core rate limiting functionality with configuration, decision-making, metrics, middleware, and service registration

- Add RateLimitConfig for configuration management with YAML binding support.
- Introduce RateLimitDecision to encapsulate the result of rate limit checks.
- Implement RateLimitMetrics for OpenTelemetry metrics tracking.
- Create RateLimitMiddleware for enforcing rate limits on incoming requests.
- Develop RateLimitService to orchestrate instance and environment rate limit checks.
- Add RateLimitServiceCollectionExtensions for dependency injection registration.

datasets/reachability/ground-truth/unreachable/gt-0011/main.c

@@ -0,0 +1,25 @@
+// gt-0011: Dead code - function never called
+// Expected: UNREACHABLE (tier: imported)
+// Vulnerability: CWE-120 (Buffer Copy without Checking Size)
+
+#include <stdio.h>
+#include <string.h>
+
+// This function is NEVER called - dead code
+void vulnerable_function(const char *input) {
+    char buffer[32];
+    strcpy(buffer, input);  // SINK: CWE-120 (but unreachable)
+    printf("Value: %s\n", buffer);
+}
+
+void safe_function(const char *input) {
+    printf("Safe: %.31s\n", input);
+}
+
+int main(int argc, char *argv[]) {
+    if (argc > 1) {
+        // Only safe_function is called
+        safe_function(argv[1]);
+    }
+    return 0;
+}