feat: Add Python SAST workflow with three security analysis tools

Implements Issue #5 - Python SAST workflow that combines:
- Dependency scanning (pip-audit) for CVE detection
- Security linting (Bandit) for vulnerability patterns
- Type checking (Mypy) for type safety issues

## Changes

**New Modules:**
- `DependencyScanner`: Scans Python dependencies for known CVEs using pip-audit
- `BanditAnalyzer`: Analyzes Python code for security issues using Bandit
- `MypyAnalyzer`: Checks Python code for type safety issues using Mypy

**New Workflow:**
- `python_sast`: Temporal workflow that orchestrates all three SAST tools
  - Runs tools in parallel for fast feedback (3-5 min vs hours for fuzzing)
  - Generates unified SARIF report with findings from all tools
  - Supports configurable severity/confidence thresholds

**Updates:**
- Added SAST dependencies to Python worker (bandit, pip-audit, mypy)
- Updated module __init__.py files to export new analyzers
- Added type_errors.py test file to vulnerable_app for Mypy validation

## Testing

Workflow tested successfully on vulnerable_app:
- ✅ Bandit: Detected 9 security issues (command injection, unsafe functions)
- ✅ Mypy: Detected 5 type errors
- ✅ DependencyScanner: Ran successfully (no CVEs in test dependencies)
- ✅ SARIF export: Generated valid SARIF with 14 total findings

test_projects/vulnerable_app/type_errors.py

@@ -0,0 +1,62 @@
+#!/usr/bin/env python3
+# Copyright (c) 2025 FuzzingLabs
+#
+# Licensed under the Business Source License 1.1 (BSL). See the LICENSE file
+# at the root of this repository for details.
+#
+# After the Change Date (four years from publication), this version of the
+# Licensed Work will be made available under the Apache License, Version 2.0.
+# See the LICENSE-APACHE file or http://www.apache.org/licenses/LICENSE-2.0
+#
+# Additional attribution and requirements are provided in the NOTICE file.
+
+"""
+Test file with type errors for Mypy testing.
+"""
+
+from typing import List, Dict
+
+
+def add_numbers(a: int, b: int) -> int:
+    """Add two integers"""
+    # Type error: returning string instead of int
+    return str(a + b)
+
+
+def process_items(items: List[str]) -> None:
+    """Process a list of strings"""
+    # Type error: iterating over None
+    for item in items:
+        print(item.upper())
+
+    # Type error: passing int to function expecting string list
+    process_items(123)
+
+
+def get_user_data() -> Dict[str, str]:
+    """Get user data"""
+    # Type error: returning wrong type
+    return ["user1", "user2"]
+
+
+def calculate_total(numbers: List[int]) -> float:
+    """Calculate total"""
+    # Type error: calling method that doesn't exist
+    return numbers.sum()
+
+
+class User:
+    def __init__(self, name: str, age: int):
+        self.name = name
+        self.age = age
+
+
+def create_user(name: str, age: int) -> User:
+    """Create a user"""
+    # Type error: returning dict instead of User
+    return {"name": name, "age": age}
+
+
+# Missing type annotations
+def unsafe_function(x, y):
+    return x + y