refactor(backend)!: separate algorithm and data layers

Reorganize algorithm packages by business responsibility, move orchestration into services, and keep database access behind pooled repositories.

Harden analysis API validation, remove unsafe legacy simulation endpoints, and add regression and architecture boundary coverage.

BREAKING CHANGE: legacy algorithm module paths and obsolete simulation endpoints are removed.

tests/unit/test_sensor_sensitivity.py

@@ -6,7 +6,7 @@ import wntr
 from scipy.sparse import csr_matrix, isspmatrix_csr
 from scipy.sparse.csgraph import dijkstra
 
-from app.algorithms.sensor import sensitivity
+from app.algorithms.pressure_sensor_placement import sensitivity_placement as sensitivity
 
 
 def _build_test_network() -> wntr.network.WaterNetworkModel: