fix: task 1.5 poster check + fix stuck tests

- Fix structlog format string in folder_scan_service (%(key)d -> kwargs)
- Add nfo_download_poster setting check before poster download
- Create missing NFO fixture files (tvshow.nfo.bad/good) for repair tests
- Fix test_context_used_in_logging to check all call args not format string
- Fix test_system_settings_integration isolation via reset_all_scans

tvshow.nfo.good

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<tvshow>
+  <title>Attack on Titan</title>
+  <originaltitle>進撃の巨人</originaltitle>
+  <year>2013</year>
+  <plot>After his hometown is destroyed and his mother is killed, young Eren Yeager vows to cleanse the earth of the giant humanoid Titans that have brought humanity to the brink of extinction.</plot>
+  <runtime>24</runtime>
+  <premiered>2013-04-07</premiered>
+  <status>Ended</status>
+  <imdbid>tt2560140</imdbid>
+  <genre>Action</genre>
+  <studio>Wit Studio</studio>
+  <country>Japan</country>
+  <actor>
+    <name>Yuki Kaji</name>
+    <role>Eren Yeager</role>
+  </actor>
+  <watched>false</watched>
+</tvshow>