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.

app/algorithms/__init__.py

@@ -1,45 +1,5 @@
-"""Algorithm package with side-effect-free, lazy compatibility exports."""
+"""Pure water-network calculation packages.
 
-from importlib import import_module
-from typing import Any
-
-
-_EXPORT_MODULES = {
-    "flow_data_clean": "app.algorithms.cleaning",
-    "pressure_data_clean": "app.algorithms.cleaning",
-    "pressure_sensor_placement_sensitivity": "app.algorithms.sensor",
-    "pressure_sensor_placement_kmeans": "app.algorithms.sensor",
-    "valve_isolation_analysis": "app.algorithms.isolation.valve",
-    "LeakageIdentifier": "app.algorithms.leakage",
-    "PipelineHealthAnalyzer": "app.algorithms.health",
-    "run_burst_location": "app.algorithms.burst_location",
-    **{
-        name: "app.algorithms.simulation.scenarios"
-        for name in (
-            "convert_to_local_unit",
-            "burst_analysis",
-            "valve_close_analysis",
-            "flushing_analysis",
-            "contaminant_simulation",
-            "age_analysis",
-            "pressure_regulation",
-        )
-    },
-}
-
-__all__ = list(_EXPORT_MODULES)
-
-
-def __getattr__(name: str) -> Any:
-    try:
-        module_name = _EXPORT_MODULES[name]
-    except KeyError as exc:
-        raise AttributeError(f"module {__name__!r} has no attribute {name!r}") from exc
-
-    value = getattr(import_module(module_name), name)
-    globals()[name] = value
-    return value
-
-
-def __dir__() -> list[str]:
-    return sorted({*globals(), *__all__})
+Application workflows belong in :mod:`app.services`; database and external
+system access belongs in :mod:`app.infra` or :mod:`app.native`.
+"""