Default to minimal blocking mode for all new users

Minimal mode has the least app breakage and is the safest default
for all builds, not just TC Slim. Users can upgrade to standard
or strict during onboarding or later in settings.

https://claude.ai/code/session_01WxVqHGC5HpTYXmqfoUpWzy

Author: claude

app/src/main/java/net/kollnig/missioncontrol/data/BlockingMode.java

@@ -78,14 +78,11 @@ public static boolean isStrictMode(Context c) {
     }
 
     /**
-     * Get the default blocking mode based on build flavor.
-     * TC Slim (play flavor) defaults to minimal mode.
+     * Get the default blocking mode for new users.
+     * Minimal is the safest default — least app breakage.
      */
     public static String getDefaultMode() {
-        if (Util.isPlayStoreInstall()) {
-            return MODE_MINIMAL;
-        }
-        return MODE_STANDARD;
+        return MODE_MINIMAL;
     }
 
     /**