Add invite buttons and /guild forceleader (#150)

* Add Accept and Decline buttons to faction and guild invites

Invites now end with clickable [Accept] and [Decline] chat buttons
instead of a typed command hint, and guild invites name the inviter
and confirm to them. /guild join and /faction join without an id
accept the only pending invite, or list several with buttons. New
/guild decline <id> and /faction decline <id> drop an invite and tell
an online leader. Guild joins announce "joined the guild" to the
realm and no longer echo to the joiner.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* Add /guild forceleader for admins

Hands a sub-guild to one of its members, like /faction forceleader
does for realms. The base guild points to /faction forceleader.
Tab completion offers sub-guild ids, then the guild's other members.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

v3.15.0 - Only regiments and vehicles stay behind the Spymaster

fix: export current passive guild cashflows (#147)

Berth a vehicle inside an installation radius even when it sits in an…

…other province.

v3.13.1 - Factions can build inside their own installations

SimpleFactions v3.11.1