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).

.pre-commit-config.yaml

@@ -6,7 +6,10 @@ repos:
         args: [--line-length=100, --target-version=py311]
 
   - repo: https://github.com/astral-sh/ruff-pre-commit
-    rev: v0.8.0
+    # Bumped from v0.8.0 so the hook recognises UP045
+    # (non-pep604-annotation-optional), which the v0.13+ ruff split off
+    # from UP007. Pyproject.toml extend-selects both rules.
+    rev: v0.15.12
     hooks:
       - id: ruff
         args: [--line-length=100, --target-version=py311]