refactor: enforce PLC0415 (import-outside-top-level) for source code

Enable ruff PLC0415 rule for all source files (tests excluded via
per-file-ignores). Move 136 inline imports to top-level across 33 files.
8 imports suppressed with noqa for legitimate reasons: circular
dependencies (client/__init__.py, context.py), optional dependency
guards (app.py document processors, auth/userinfo_routes.py), and
post-env-setup imports (smithery_main.py).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -106,7 +106,10 @@ changelog_pattern = "^(feat|fix|docs|refactor|perf|test|build|ci|chore)(?!\\((?:
 schema_pattern = "^(feat|fix|docs|refactor|perf|test|build|ci|chore)(?!\\((?:helm)\\))(\\([^)]+\\))?(!)?:\\s.+"
 
 [tool.ruff.lint]
-extend-select = ["I"]
+extend-select = ["I", "PLC0415"]
+
+[tool.ruff.lint.per-file-ignores]
+"tests/**" = ["PLC0415"]
 
 [tool.uv.sources]
 caldav = { git = "https://github.com/cbcoutinho/caldav", branch = "feature/httpx" }