security: fix high-severity security issues

- Remove hardcoded passwords in wallet commands (2 instances)
- Fix SQL injection vectors with parameterized queries (3 instances)
- Replace MD5 hashes with SHA-256 in 14 locations
- Add table name validation in migration scripts

dev/gpu_acceleration/cuda_kernels/gpu_aware_compiler.py

@@ -296,7 +296,7 @@ class GPUAwareCompiler:
             
         except Exception:
             # Fallback to filename
-            return hashlib.md5(str(circuit_path).encode()).hexdigest()[:16]
+            return hashlib.sha256(str(circuit_path).encode()).hexdigest()[:16]
     
     def _load_cache(self, cache_path: Path) -> Optional[Dict]:
         """Load cached compilation result"""