Activity flow: tolerate cyclic flows; Lifecycle tab: inline save button

[roncodes]

Summary

Follow-up to #350.

• Activity Flow crashed on cyclic flows. addChildActivities walked the flow as a tree and recursed forever when a configured lifecycle loops back (the RSA Loan config has active → extended → active), until JointJS overflowed the stack (Invalid regular expression ... Stack overflow from delegateEvents) when opening the Activity Flow tab. An activity already on the graph now only receives a link from the additional parent and is not placed or walked again. This also covers an activity reachable from several parents.
• Lifecycle tab: the save button sits under the form instead of in a separate collapsible "Controls" panel.

Test plan

• Open the Activity Flow tab of a config whose flow has a cycle (e.g. the Porsche RSA Loan config) — it renders, with a back-link, instead of crashing.
• Lifecycle tab: edit and save still works; the save button is under the form.