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>

nextcloud_mcp_server/auth/browser_oauth_routes.py

@@ -11,6 +11,7 @@ import secrets
 import time
 from base64 import urlsafe_b64encode
 from urllib.parse import urlencode
+from urllib.parse import urlparse as parse_url
 
 import httpx
 import jwt
@@ -153,8 +154,6 @@ async def oauth_login(request: Request) -> RedirectResponse | JSONResponse:
         # Replace internal Docker hostname with public URL
         public_issuer = os.getenv("NEXTCLOUD_PUBLIC_ISSUER_URL")
         if public_issuer:
-            from urllib.parse import urlparse as parse_url
-
             internal_parsed = parse_url(oauth_config["nextcloud_host"])
             auth_parsed = parse_url(authorization_endpoint)