refactor(types): PEP-604 union sweep + UP007/UP045 enforcement

ruff --select UP007,UP045 --fix converted ~1760 sites across the
backend: `Optional[T]` → `T | None`, `Union[X, Y]` → `X | Y`. The
remaining module-level alias targets that ruff conservatively skips
(BindableFloatInput, ColorList, DeviceConfig) were converted by hand
earlier in the pass. black -formatted the result so the wider unions
fit cleanly under the 100-char line budget.

pyproject.toml now sets [tool.ruff.lint] extend-select = ["UP007",
"UP045"] so future legacy imports fire CI on every push. The
pre-commit ruff hook was bumped from v0.8.0 -> v0.15.12 to recognise
UP045 (split off from UP007 in v0.13).

server/pyproject.toml

@@ -117,3 +117,11 @@ target-version = ['py311']
 [tool.ruff]
 line-length = 100
 target-version = "py311"
+
+[tool.ruff.lint]
+# E + F are ruff's defaults; UP007 + UP045 enforce PEP-604 `X | Y` and
+# `T | None` style so we don't drift back to the legacy `Union[X, Y]` /
+# `Optional[T]` imports the REVIEW_TODO mechanical sweep removed.
+# Recent ruff versions split the rule — UP007 covers `Union`, UP045
+# covers `Optional`.
+extend-select = ["UP007", "UP045"]