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/basic/gt-0003/main.c

@@ -0,0 +1,25 @@
+// gt-0003: Three-hop call chain with command injection
+// Expected: REACHABLE (tier: executed)
+// Vulnerability: CWE-78 (OS Command Injection)
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+void execute_command(const char *cmd) {
+    // Vulnerable: system call with user input
+    system(cmd);  // SINK: CWE-78
+}
+
+void process_input(const char *input) {
+    char command[256];
+    snprintf(command, sizeof(command), "echo %s", input);
+    execute_command(command);
+}
+
+int main(int argc, char *argv[]) {
+    if (argc > 1) {
+        process_input(argv[1]);
+    }
+    return 0;
+}