outsourced lots of api calls to api folder

centered error message when failed loading video feed
display server url on settings page

lib/db/database.dart

@@ -25,12 +25,8 @@ class Db {
     }
 
     _db = await openDatabase(
-      // Set the path to the database. Note: Using the `join` function from the
-      // `path` package is best practice to ensure the path is correctly
-      // constructed for each platform.
       dbpath,
       onCreate: (db, version) {
-        // Run the CREATE TABLE statement on the database.
         return db.execute(
           'CREATE TABLE previews(id INTEGER PRIMARY KEY, thumbnail BLOB)',
         );