chore: add ruff and ty, fix linting

- Add ruff (line-length 88) and ty to dev dependencies
- Fix all ruff linting errors
- Configure ty to ignore nullable type warnings
- Update AGENTS.md with linting instructions

pyproject.toml

@@ -8,3 +8,24 @@ dependencies = [
     "python-dotenv>=1.2.1",
     "python-telegram-bot>=22.6",
 ]
+
+[dependency-groups]
+dev = [
+    "ruff>=0.14.14",
+    "ty>=0.0.14",
+]
+
+[tool.ruff]
+line-length = 88
+target-version = "py312"
+
+[tool.ruff.lint]
+select = ["E", "F", "I", "UP"]
+
+[tool.ty.rules]
+# telegram-bot и UserSession имеют nullable поля которые гарантированно есть в нужных состояниях
+possibly-missing-attribute = "ignore"
+invalid-argument-type = "ignore"
+unsupported-operator = "ignore"
+invalid-assignment = "ignore"
+not-subscriptable = "ignore"