Hide changed connection lines behind -v/--verbose

set_local_db/set_dot_env diffs can contain secrets (connection
strings), so printing them unconditionally on every up/down leaked
credentials to stdout. Default output is now a line-count summary;
pass -v/--verbose to see the actual before/after lines.

src/arguments.rs

@@ -13,6 +13,13 @@ pub struct Arguments {
 
     #[arg(help = "Possible values are 'up' and 'down'")]
     pub action: String,
+
+    #[arg(
+        short,
+        long,
+        help = "Show which lines were changed (values may include secrets)"
+    )]
+    pub verbose: bool,
 }
 
 impl Arguments {
@@ -33,6 +40,7 @@ mod tests {
         Arguments {
             project: "test".to_string(),
             action: action.to_string(),
+            verbose: false,
         }
     }