feat: guide missing external network creation during deploy (#1645)

* feat: guide missing external network creation during deploy

Detect missing external networks before Compose runs, prompt or auto-create safe bridge networks, and keep unsupported declarations blocked with trusted deploy provenance.

* test: align deploy context and settings fixtures with missing-network gate

Update caller spies, EffResource expectations, StacksSection save keys, and git-source spy cleanup so CI matches the new deployStack context and auto-create setting.

* fix: drop unused renderError binding in missing-network resolver

Satisfies no-unused-vars so backend ESLint CI passes; callers already key only on model presence.

* fix: use HTTP-safe clipboard helper in missing-network dialog

navigator.clipboard fails on plain HTTP LAN hosts; route copy actions through copyToClipboard so Docker and Compose copy buttons work on self-hosted instances.

* fix: simplify missing-network dialog actions and copy label

Drop the Compose snippet escape hatch, move secondary actions under More, and rename the terminal copy action to Copy create command so the footer is a clear Cancel / Create decision.

docs/reference/settings.mdx

@@ -675,6 +675,7 @@ Node-level safety checks and post-deploy observation used during stack deploys a
 | **Observe health after updates** | On | After a stack deploy or update succeeds, watch its containers for the observation window and record a passed or failed verdict on the stack timeline. Observational only: nothing is restarted or rolled back automatically. |
 | **Observation window** | 90 s | How long to watch containers before declaring the update healthy. Raise it for stacks that take a while to settle. Range 15 to 600 seconds. |
 | **Block deploy on missing required env vars** | Off | When on, a deploy or update is refused before it starts if a required `${VAR:?message}` variable is unset or empty, so the stack fails fast with a clear message instead of mid-deploy. |
+| **Automatically create missing external networks during deploy** | Off | When on, safe missing external bridge networks are created automatically before deploy continues. When off, interactive deploy prompts first. Advanced drivers and custom options are never auto-created. |
 
 Click **Save settings** to apply.