Add multi-language AST-pattern scanning support

- Introduced `patterns` module with language-specific vulnerability patterns.
- Added `query_cache` utility for caching compiled queries.
- Expanded `scan.rs` to support scanning multiple languages dynamically.
- Updated `Cargo.toml` with additional tree-sitter dependencies.
- Added severity filtering to `ScannerConfig` for better configuration.

src/patterns/cpp.rs

@@ -0,0 +1,40 @@
+use crate::patterns::{Pattern, Severity};
+
+pub const PATTERNS: &[Pattern] = &[
+  Pattern {
+    id: "strcpy_call",
+    description: "strcpy() usage",
+    query: "(call_expression function: (identifier) @id (#eq? @id \"strcpy\")) @vuln",
+    severity: Severity::High,
+  },
+  Pattern {
+    id: "strcat_call",
+    description: "strcat() usage",
+    query: "(call_expression function: (identifier) @id (#eq? @id \"strcat\")) @vuln",
+    severity: Severity::High,
+  },
+  Pattern {
+    id: "sprintf_call",
+    description: "sprintf() (no length limit)",
+    query: "(call_expression function: (identifier) @id (#eq? @id \"sprintf\")) @vuln",
+    severity: Severity::High,
+  },
+  Pattern {
+    id: "gets_call",
+    description: "gets() usage",
+    query: "(call_expression function: (identifier) @id (#eq? @id \"gets\")) @vuln",
+    severity: Severity::High,
+  },
+  Pattern {
+    id: "system_call",
+    description: "system() shell execution",
+    query: "(call_expression function: (identifier) @id (#eq? @id \"system\")) @vuln",
+    severity: Severity::Medium,
+  },
+  Pattern {
+    id: "reinterpret_cast",
+    description: "reinterpret_cast usage",
+    query: "(reinterpret_cast_expression) @vuln",
+    severity: Severity::Medium,
+  },
+];