feat!: distinguish URLs and hosts

BREAKING CHANGE: the configuration for Bitmagnet and Ntfy has changed.
Instead of `host`, they now use `url`.

src/config/fixtures/test_config.toml

@@ -1,6 +1,6 @@
 [bitmagnet]
 enable = true
-host = "http://localhost:8080"
+url = "http://localhost:8080"
 
 [transmission]
 enable = false
@@ -13,7 +13,7 @@ download_dir = "/downloads"
 [ntfy]
 enable = true
 topic = "reddit-magnet"
-host = "https://ntfy.sh"
+url = "https://ntfy.sh"
 priority = "default"
 
 [sources.movies]
@@ -25,4 +25,4 @@ tags = ["movies", "hd"]
 username = "tv_shows_fan"
 title_filter = "S\\d{2}E\\d{2}"
 imdb_id = "tt1234567"
-tags = ["tv", "series"]
+tags = ["tv", "series"]