[P2][Plan 5] SF-020 — Simplify model setup for first-time users

[Ankit6149]

Confirmed problem

A normal user is immediately shown providers, temporary keys, base URLs, model overrides, server configuration, and local/self-hosted concepts. The setup feels like developer infrastructure rather than the shortest path to a successful campaign.

Scope

• Default to a recommended provider route.
• Keep the primary flow to provider, temporary key when needed, Test connection, and Continue.
• Move base URL, model override, custom gateway, Ollama, and LM Studio into Advanced model settings.
• Show owner/server-configured routes only when the current session may use them.
• Explain local reachability and credential handling in plain language.

Acceptance criteria

• A first-time user can configure a supported provider without understanding endpoints or model IDs.
• Advanced controls remain available without competing with the primary action.
• Temporary keys are never persisted.
• Recommended selection is based on actual session/provider readiness.
• Test connection failures provide actionable provider-specific guidance.

Required verification

• First-run usability flow for owner and non-owner sessions.
• Provider readiness and permission tests.
• Keyboard/mobile/long-error rendering tests.