fix(backend): Combo Control Center: 'Configured targets' hides the model and truncates the account

Bug

In the Combo Control Center (/dashboard/combos/<id>), the Configured targets card does not show which model each target uses, and the pinned account is truncated.

Current behavior

• The primary line renders target.label. For steps created by the combo builder with a pinned account, label stores the account label (set by buildPrecisionComboModelStep in src/lib/combos/builderDraft.ts), so the row shows provider + account but never the model name.
• The account renders as account {id} via shortId(connectionId) → first 10 chars + …, so the account is unreadable/cut off.

Example today:

1  Model target
user@example.com          <- account label, not the model
OpenAI · account abc1234…

Expected behavior

1  Model target
openai/gpt-5-codex        <- the configured model
OpenAI · account user@example.com   <- full account, no truncation

• Show the configured model (provider/model) for model steps, the combo name for combo-ref, and provider/pattern for provider-wildcard targets.
• Show the full account: resolve the connection display name (name/displayName/email, same getAccountDisplayName source the combo builder uses); fall back to the stored step label, then to the full untruncated connectionId, and dynamic when no connection is pinned.

Scope

src/app/(dashboard)/dashboard/combos/ComboControlCenterClient.tsx (TargetConfiguredRow) + account-name resolution helper in src/lib/combos/controlCenter.ts.