prevent running migrations if is_fresh_install

+ fix: sqlite3.ProgrammingError: Cannot operate on a closed cursor on ProcessAlbumColors()
+ move processing artist images from periodic_scans to Populate
+ bump hash string limit from 7 to 10
+ add last_mod property to database
+ fix: TypeError: '<' not supported between instances of 'int' and 'str' on album page

app/migrations/__init__.py

@@ -24,6 +24,10 @@ def apply_migrations():
     userdb_version = MigrationManager.get_userdatadb_postinit_version()
     maindb_version = MigrationManager.get_maindb_postinit_version()
 
+    # No migrations to run
+    if userdb_version == 0 and maindb_version == 0:
+        return
+
     for migration in main_db_migrations:
         if migration.version > maindb_version:
             log.info("Running new MAIN-DB post-init migration: %s", migration.name)