fix: resolve all 64 mypy errors across backend

- Add dict[str, Any] / list[Any] type params throughout (fingerprint, models, schemas, scanner, status_checker)
- Add return type annotations to all route functions (nodes, edges, canvas, scan, auth, status, main)
- Fix no-any-return in security.py: cast pwd/jwt results to bool/str explicitly
- Fix canvas.py: use model_validate() for NodeResponse/EdgeResponse, rename db_node/db_edge upsert vars
- Fix scheduler.py: rename 'result' → 'check_result' to avoid type collision
- Fix get_db() return type: AsyncGenerator[AsyncSession, None]
- Add types-PyYAML for yaml import stubs
- Fix scanner.py: remove unnecessary type: ignore comment (nmap has stubs)
- Fix scan.py: wrap scalars().all() with list() for Sequence→list compatibility

backend/app/core/security.py

@@ -9,22 +9,23 @@ pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
 
 
 def verify_password(plain: str, hashed: str) -> bool:
-    return pwd_context.verify(plain, hashed)
+    return bool(pwd_context.verify(plain, hashed))
 
 
 def hash_password(password: str) -> str:
-    return pwd_context.hash(password)
+    return str(pwd_context.hash(password))
 
 
 def create_access_token(subject: str) -> str:
     expire = datetime.now(UTC) + timedelta(minutes=settings.access_token_expire_minutes)
     payload = {"sub": subject, "exp": expire}
-    return jwt.encode(payload, settings.secret_key, algorithm=settings.algorithm)
+    return str(jwt.encode(payload, settings.secret_key, algorithm=settings.algorithm))
 
 
 def decode_token(token: str) -> str | None:
     try:
         payload = jwt.decode(token, settings.secret_key, algorithms=[settings.algorithm])
-        return payload.get("sub")
+        sub = payload.get("sub")
+        return str(sub) if sub is not None else None
     except JWTError:
         return None