Enhance UI rendering and add unit tests for simulation functionality

- Updated the `_render` function in `ui.py` to correctly pass the request object to `TemplateResponse`.
- Initialized `upcoming_maintenance` as a typed list in `_load_dashboard` for better type safety.
- Added new unit tests in `test_simulation.py` to cover triangular sampling and uniform distribution defaults.
- Implemented a test to ensure that running the simulation without parameters returns an empty result.
- Created a parameterized test in `test_ui_routes.py` to verify that additional UI routes render the correct templates and context.

tests/unit/test_simulation.py

@@ -1,3 +1,5 @@
+from math import isclose
+from random import Random
 from uuid import uuid4
 
 import pytest
@@ -7,7 +9,7 @@ from sqlalchemy.orm import Session
 from typing import Any, Dict, List
 
 from models.simulation_result import SimulationResult
-from services.simulation import run_simulation
+from services.simulation import DEFAULT_UNIFORM_SPAN_RATIO, run_simulation
 
 
 @pytest.fixture
@@ -97,6 +99,46 @@ def test_run_simulation_normal_std_dev_fallback():
     assert all("result" in entry for entry in results)
 
 
+def test_run_simulation_triangular_sampling_path():
+    params: List[Dict[str, Any]] = [
+        {"name": "tri", "value": 10.0, "distribution": "triangular"}
+    ]
+    seed = 21
+    iterations = 4
+    results = run_simulation(params, iterations=iterations, seed=seed)
+    assert len(results) == iterations
+    span = 10.0 * DEFAULT_UNIFORM_SPAN_RATIO
+    rng = Random(seed)
+    expected_samples = [
+        rng.triangular(10.0 - span, 10.0 + span, 10.0) for _ in range(iterations)
+    ]
+    actual_samples = [entry["result"] for entry in results]
+    for actual, expected in zip(actual_samples, expected_samples):
+        assert isclose(actual, expected, rel_tol=1e-9)
+
+
+def test_run_simulation_uniform_defaults_apply_bounds():
+    params: List[Dict[str, Any]] = [
+        {"name": "uniform-auto", "value": 200.0, "distribution": "uniform"}
+    ]
+    seed = 17
+    iterations = 3
+    results = run_simulation(params, iterations=iterations, seed=seed)
+    assert len(results) == iterations
+    span = 200.0 * DEFAULT_UNIFORM_SPAN_RATIO
+    rng = Random(seed)
+    expected_samples = [
+        rng.uniform(200.0 - span, 200.0 + span) for _ in range(iterations)
+    ]
+    actual_samples = [entry["result"] for entry in results]
+    for actual, expected in zip(actual_samples, expected_samples):
+        assert isclose(actual, expected, rel_tol=1e-9)
+
+
+def test_run_simulation_without_parameters_returns_empty():
+    assert run_simulation([], iterations=5) == []
+
+
 def test_simulation_endpoint_no_params(client: TestClient):
     scenario_payload: Dict[str, Any] = {
         "name": f"NoParamScenario-{uuid4()}",