feat(app-dev): add dry-run preview to dev sync (#21251)

Split out of #21240. Stacked on #21250 (review/merge that first).

`yarn twenty dev --once --dry-run` computes the migration plan and
prints the diff **without applying anything** (no migration, no
app-record update, no SDK generation). Also renders the diff on a normal
`dev --once` sync.

<img width="646" height="179" alt="image"
src="https://github.com/user-attachments/assets/59f3ddcd-2a5b-4b8a-b21a-c659abe16af0"
/>

packages/twenty-sdk/src/cli/commands/dev/index.ts

@@ -22,6 +22,7 @@ export const registerDevCommands = (program: Command): void => {
       verbose?: boolean;
       debug?: boolean;
       debounceMs?: string;
+      dryRun?: boolean;
     },
   ) => {
     const commonOptions = {
@@ -33,7 +34,10 @@ export const registerDevCommands = (program: Command): void => {
     };
 
     if (options.once) {
-      await devOnceCommand.execute(commonOptions);
+      await devOnceCommand.execute({
+        ...commonOptions,
+        dryRun: options.dryRun,
+      });
 
       return;
     }
@@ -48,6 +52,10 @@ export const registerDevCommands = (program: Command): void => {
       '-o, --once',
       'Build and sync once, then exit (useful for CI, scripts, and pre-commit hooks)',
     )
+    .option(
+      '--dry-run',
+      'Preview the metadata changes without applying them (requires --once)',
+    )
     .option('--debounceMs <ms>', 'Debounce in ms (default: 2 000)')
     .option('-v, --verbose', 'Show detailed logs')
     .option('-d, --debug', 'Show detailed logs (alias for --verbose)')