Backend test hardening + quality enforcement (#872)

- Reworked many tests
- Enforcing lint + type checking for test suite
- Fixed various issues surfaced by the new tests
- CI tweaks

pyproject.toml

@@ -95,10 +95,36 @@ ignore = ["D", "EM", "FBT", "PLR2004", "UP035", "TRY003", "E501", "TD002", "S104
 [tool.ruff.lint.per-file-ignores]
 "tests/**/*.py" = [
     "ANN",
-    "S101",
-    "S105",
-    "S108",
-    "S311",
+    "BLE001",
+    "B010",
+    "B017",
+    "B028",
+    "DTZ",
+    "E402",
+    "E731",
+    "ERA001",
+    "FURB",
+    "G003",
+    "G004",
+    "PERF",
+    "PIE",
+    "PLC0414",
+    "PLW0108",
+    "PLW1510",
+    "PLW2901",
+    "PTH",
+    "PT028",
+    "PYI034",
+    "Q000",
+    "RET",
+    "RUF012",
+    "S",
+    "SIM",
+    "TC001",
+    "TC002",
+    "TC003",
+    "TRY",
+    "UP028",
 ]
 
 [tool.basedpyright]