chore: add ruff linter/formatter for Python server

- Add ruff>=0.11.0 as dev dependency via [dependency-groups]
- Configure [tool.ruff]: line-length=100, py310 target, LF line endings
- Lint rules: E, F, UP, B, SIM, I (ignoring E501/B905)
- Add lint:server and lint:server:fix scripts to root package.json
- Update format/format:check to also run ruff for server/

server/pyproject.toml

@@ -19,10 +19,36 @@ dependencies = [
     "huggingface_hub>=0.23.0",
 ]
 
+[dependency-groups]
+dev = [
+    "ruff>=0.11.0",
+]
+
 # No build-system — this is a scripts project, not an installable package.
 # Lock file is committed so installs are reproducible.
 # Run `uv lock --upgrade` to bump dependencies.
 
+[tool.ruff]
+line-length = 100
+indent-width = 4
+target-version = "py310"
+exclude = [".git", ".venv", ".venv-cpu", "__pycache__"]
+
+[tool.ruff.lint]
+select = ["E", "F", "UP", "B", "SIM", "I"]
+ignore = [
+    "E501",  # line-too-long — handled by formatter
+    "B905",  # zip() without strict= — existing code, lengths are known-correct
+]
+
+[tool.ruff.lint.per-file-ignores]
+"download_model.py" = ["T201"]  # allow print statements in CLI scripts
+
+[tool.ruff.format]
+quote-style = "double"
+indent-style = "space"
+line-ending = "lf"
+
 [[tool.uv.index]]
 name = "pytorch-cu124"
 url = "https://download.pytorch.org/whl/cu124"