chore: add Ruff and apply formatting across codebase

Introduce ruff lint/format config, expand .gitignore, and reformat Python sources.

Co-authored-by: Cursor <cursoragent@cursor.com>

pyproject.toml

@@ -10,11 +10,17 @@ readme = "README.md"
 requires-python = ">=3.11"
 license = { text = "MIT" }
 authors = [{ name = "Frank" }]
-dependencies = []
+dependencies = [
+    "Pillow>=10.0",
+]
 
 [project.optional-dependencies]
-ai = ["numpy>=1.26", "Pillow>=10.0", "torch>=2.0"]
-dev = ["pytest>=8.0"]
+ai = ["numpy>=1.26", "torch>=2.0"]
+dev = [
+    "pytest>=8.0",
+    "numpy>=1.26",
+    "ruff>=0.8",
+]
 
 [project.scripts]
 imagepipeline = "imagepipeline.cli:main"
@@ -25,3 +31,28 @@ include = ["imagepipeline*"]
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]
+markers = [
+    "integration: tests that call external CLI tools (ImageMagick, G'MIC, rembg, darktable, GIMP)",
+    "slow: tests that take more than a few seconds",
+]
+
+[tool.ruff]
+target-version = "py311"
+line-length = 100
+src = ["imagepipeline", "tests", "pipelines"]
+
+[tool.ruff.lint]
+select = [
+    "E",   # pycodestyle errors
+    "F",   # pyflakes
+    "I",   # isort
+    "UP",  # pyupgrade
+    "B",   # flake8-bugbear
+]
+ignore = [
+    "E501",  # line length handled by formatter
+    "B027",  # optional empty hooks on BaseModule
+]
+
+[tool.ruff.lint.isort]
+known-first-party = ["imagepipeline"]