feat(app-dev): sync error hints, flatEntity labels, dev-mode summary UI, and docs (#21252)

Split out of #21240 — all remaining app-dev improvements. Stacked on
#21251 (review/merge that first).

- Actionable recovery hints on failed syncs; unified diff renderer;
`--dry-run` guard.
- Return `flatEntity` on update/delete sync actions and unify the diff
label.
- Summarize the dev-mode entity list unless `--verbose`.
- Docs: syncing & recovery guide + dry-run + open-an-issue prompt.
- Live execution mode for synced logic functions; clearer manifest
warnings.

<img width="1018" height="700" alt="image"
src="https://github.com/user-attachments/assets/5e9ce19e-0f1d-4f99-8524-4e118bde932b"
/>

packages/twenty-docs/navigation/base-structure.json

@@ -431,6 +431,7 @@
               "pages": [
                 "developers/extend/apps/operations/overview",
                 "developers/extend/apps/operations/cli",
+                "developers/extend/apps/operations/sync-and-recovery",
                 "developers/extend/apps/operations/testing",
                 "developers/extend/apps/operations/publishing"
               ]