chore: bump sdk packages to 2.19.0-alpha.1 prerelease (#22599)

## Summary

- Bumps `twenty-sdk`, `twenty-client-sdk` and `create-twenty-app` from
`2.19.0` to `2.19.0-alpha.1` so the CD pipeline can publish a prerelease
of the SDK.

## Context

#22565 made system field universal identifiers deterministic and
fail-closed: any app package built with SDK ≤ 2.18 carries legacy system
field identifiers in its `manifest.json` and is now rejected at
install/sync time on servers running `main`. Rebuilding the apps
requires a published SDK carrying the new derivation.

Publishing `2.19.0-alpha.1` lets us rebuild all apps in
`packages/twenty-apps` (follow-up PR) against the new derivation while
keeping `latest` on `2.18.0` for authors targeting prod, which has not
run the 2.19 backfill yet.

⚠️ The publish job must tag this prerelease under a non-`latest`
dist-tag (e.g. `next`): the server resolves app installs and the upgrade
version check against the `latest` dist-tag.

Server version constants (`TWENTY_CURRENT_VERSION`, etc.) are
intentionally untouched.

## Test plan

- [ ] Verify the three package versions are `2.19.0-alpha.1`
- [ ] Verify the publish workflow in the CD repo tags the release as
`next` (not `latest`)

Made with [Cursor](https://cursor.com)

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packages/create-twenty-app/package.json

@@ -1,6 +1,6 @@
 {
   "name": "create-twenty-app",
-  "version": "2.19.0",
+  "version": "2.19.0-alpha.1",
   "description": "Command-line interface to create Twenty application",
   "main": "dist/cli.cjs",
   "bin": "dist/cli.cjs",

packages/twenty-client-sdk/package.json

@@ -1,6 +1,6 @@
 {
   "name": "twenty-client-sdk",
-  "version": "2.19.0",
+  "version": "2.19.0-alpha.1",
   "sideEffects": false,
   "license": "AGPL-3.0",
   "scripts": {

packages/twenty-sdk/package.json

@@ -1,6 +1,6 @@
 {
   "name": "twenty-sdk",
-  "version": "2.19.0",
+  "version": "2.19.0-alpha.1",
   "sideEffects": false,
   "bin": {
     "twenty": "dist/cli.cjs"