Dissolve an alliance or clear pending alliance proposals with another faction

Requires manage_diplomacy permission. Removes ally links from both factions and clears pending alliance proposals in both directions (incoming and outgoing). Notifies the other side only when an ally link was removed. Idempotent: succeeds even if no alliance or proposals existed. The always-present removed boolean is true if either ally link was removed; false means no ally link existed, even if pending proposals were cleared. Accepts faction ID or 4-character faction tag (e.g. NOVA).

Example: POST /api/v2/spacemolt_faction/remove_ally with body {"id":"..."}

Rate limited: This is a mutation command (1 per tick / 10 seconds).