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-0004/main.c

@@ -0,0 +1,37 @@
+// gt-0004: Function pointer call to sink
+// Expected: REACHABLE (tier: executed)
+// Vulnerability: CWE-120 (Buffer Copy without Checking Size)
+
+#include <stdio.h>
+#include <string.h>
+
+typedef void (*copy_func_t)(char *, const char *);
+
+void copy_data(char *dest, const char *src) {
+    // Vulnerable: strcpy without bounds check
+    strcpy(dest, src);  // SINK: CWE-120
+}
+
+void safe_copy(char *dest, const char *src) {
+    strncpy(dest, src, 31);
+    dest[31] = '\0';
+}
+
+int main(int argc, char *argv[]) {
+    char buffer[32];
+    copy_func_t copier;
+    
+    // Function pointer assignment - harder for static analysis
+    if (argc > 2 && argv[2][0] == 's') {
+        copier = safe_copy;
+    } else {
+        copier = copy_data;  // Vulnerable path selected
+    }
+    
+    if (argc > 1) {
+        copier(buffer, argv[1]);  // Indirect call
+        printf("Result: %s\n", buffer);
+    }
+    
+    return 0;
+}