Consolidate contact Manage into a single inline panel

[alexeygrigorev]

Part of UX epic #67. From the operator UX audit (finding 11, MEDIUM).

Problem

"Manage contact" anchor-jumps to a collapsed <details> at the very bottom containing four separate mini-forms (State / Subscription / Add tag / Remove tag). Fixing a subscription means a lot of scrolling and clicking. (contact_detail.html:22,159-186)

Ask

Keep summary-first structure but surface a single consolidated Manage panel (or place subscription controls next to the Subscriptions section) so the common fix is one action.

Acceptance

• Common contact management actions reachable without hunting to page bottom.
• Tests + lint pass.