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-0002/main.c

@@ -0,0 +1,22 @@
+// gt-0002: Two-hop call chain to vulnerable sink
+// Expected: REACHABLE (tier: executed)
+// Vulnerability: CWE-134 (Format String)
+
+#include <stdio.h>
+#include <string.h>
+
+void format_message(const char *user_input, char *output) {
+    // Vulnerable: format string from user input
+    sprintf(output, user_input);  // SINK: CWE-134
+}
+
+int main(int argc, char *argv[]) {
+    char buffer[256];
+    
+    if (argc > 1) {
+        format_message(argv[1], buffer);
+        printf("Result: %s\n", buffer);
+    }
+    
+    return 0;
+}

datasets/reachability/ground-truth/basic/gt-0002/sample.manifest.json

@@ -0,0 +1,30 @@
+{
+  "$schema": "https://stellaops.io/schemas/sample-manifest.v1.json",
+  "sampleId": "gt-0002",
+  "version": "1.0.0",
+  "category": "basic",
+  "description": "Two-hop call chain to vulnerable sink - REACHABLE",
+  "language": "c",
+  "expectedResult": {
+    "reachable": true,
+    "tier": "executed",
+    "confidence": 1.0
+  },
+  "source": {
+    "files": ["main.c"],
+    "entrypoint": "main",
+    "sink": "sprintf",
+    "vulnerability": "CWE-134"
+  },
+  "callChain": [
+    {"function": "main", "file": "main.c", "line": 15},
+    {"function": "format_message", "file": "main.c", "line": 7},
+    {"function": "sprintf", "file": "<libc>", "line": null}
+  ],
+  "annotations": {
+    "notes": "Two-hop chain: main -> helper -> sink",
+    "difficulty": "easy"
+  },
+  "createdAt": "2025-12-17T00:00:00Z",
+  "createdBy": "corpus-team"
+}