chore(apps): move public apps to packages/twenty-apps/public and generalize CI workflow (#22096)

## What

Introduces a `packages/twenty-apps/public/` folder and moves the
publicly publishable apps into it, then generalizes the apps CI workflow
to cover both folders.

### Moves
The following apps were moved from `packages/twenty-apps/internal/` to
`packages/twenty-apps/public/` (via `git mv`, history preserved):
- `people-data-labs`
- `twenty-discord`
- `twenty-exa`
- `twenty-fireflies`
- `twenty-last-contact`
- `twenty-linear`
- `twenty-meeting-bot`
- `twenty-slack`

These remain in `internal/`: `self-hosting`, `twenty-for-twenty`,
`twenty-partners`.

### Workflow
- Renamed `.github/workflows/ci-internal-apps.yaml` →
`.github/workflows/ci-twenty-apps.yaml`.
- The discover job now scans **both** `packages/twenty-apps/internal`
and `packages/twenty-apps/public`:
  - the "no nested `.github`" guard checks both folders,
  - `changed-files` watches both globs,
- the matrix builder iterates over both roots (guarded with `existsSync`
so a missing folder is a no-op).
- Each matrix entry still carries its own `path`, so the `ci` job works
unchanged regardless of which folder an app lives in.

## Notes
- The apps are standalone packages (own `yarn.lock`, not part of the
root Nx workspaces), so no root `package.json` / `nx.json` / `tsconfig`
changes were needed.
- The companion publish workflow lives in `twentyhq/twenty-infra`
(`publish-internal-apps.yaml` → `publish-public-apps.yaml`) and is
updated in a paired PR.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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.github/dependabot.yml

@@ -18,3 +18,28 @@ updates:
       # chokidar is pinned to v3 via a resolution: v4+ dropped native macOS
       # FSEvents and hits EMFILE on a repo this size (see #20316)
       - dependency-name: "chokidar"
+  # Public Twenty apps are standalone packages (own lockfiles) excluded from the
+  # root entry above. Each app folder is updated weekly, grouped into a single PR.
+  - package-ecosystem: "npm"
+    directories:
+      - "/packages/twenty-apps/public/*"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 3
+    versioning-strategy: "lockfile-only"
+    groups:
+      twenty-apps-public:
+        patterns:
+          - "*"
+  # Internal Twenty apps, same treatment as the public apps above.
+  - package-ecosystem: "npm"
+    directories:
+      - "/packages/twenty-apps/internal/*"
+    schedule:
+      interval: "weekly"
+    open-pull-requests-limit: 3
+    versioning-strategy: "lockfile-only"
+    groups:
+      twenty-apps-internal:
+        patterns:
+          - "*"