Add invites & join-requests admin sections to the Collaboration view (#241)

[mstomar125]

Slice S4 of the collection-membership-UI epic (NodeSpaceAI/nodespace-sync#237) — invite & request management in the Collaboration view.

Stacked on #1474 (S3) → #1473 (S1). Cross-fork PRs base on main, so the diff includes the S1+S3 commits until they merge — review the top commit (Add invites & join-requests…). I'll rebase as the parents land.

What

Extends the S3 Collaboration view with two admin-only sections (gated on the caller's own admin role; consumes the invites/requests the S1 store already loads for admins):

Invites

• Create an invite with a role, optional email binding, and a TTL preset (1 day / 7 days / never) → pro_create_invite.
• A bearer (no-email) invite surfaces its share code with a copy button; an email-bound invite is delivered to that address (no code shown).
• Pending-invites list with per-invite copy-code and revoke → pro_revoke_invite.

Join requests

• List pending requests; approve with a selectable role → pro_approve_request, or reject → pro_revoke_invite (via the store's rejectRequest).

Tests

• 4 new component tests (admin-only section gating; bearer-invite create with default role/TTL + code surfaced; revoke; approve-with-selected-role + reject). 9 total in collaboration-view.test.ts.
• bun run quality:fix — ESLint 0/0, svelte-check 0 errors.

Depends on S1 (#238) + S2 (#239). Part of #241.

[mstomar125]

APPROVE — S4 admin sections (invites + join-requests) are well-implemented and correctly gated; one load-bearing merge-order requirement below.

Verified against code at head 2a6d4d08:

Free-user mandate — intact. collaboration-view.svelte is only ever mounted from the collection-node-viewer's {#if proSync.isPro} branch (the S3/#1474 tab strip I verified earlier is +49/-0 with an {:else} preserving the original .collection-content). The new Invites/Join-requests sections render only when amAdmin is true, so a Pro non-admin sees the roster only. All service calls hit pro_* commands. Error handling + busy-state guards on all actions; approve passes the selected role through; reject correctly reuses revoke_invite. Tests pin the admin-vs-non-admin gating and the action flows.

⚠️ Merge-order (blocking on ordering, not on code): this branch is stacked on the pre-fix S1 commit 90efb7c3, not #1473's fixed head dd8ec94e. So its stores/membership.svelte.ts is still the un-guarded version — requirePro() absent, acceptInvite/requestJoin (:191/:196) and the other mutations lack the !isPro guard that #1473 added. This branch must rebase onto #1473 (dd8ec94e) / main-after-#1473 before merging — do not merge the raw branch ahead of #1473 or it regresses the community-inert store fix.

Good news: this is rebase-safe. #1475's own commit (2a6d4d08) changes only collaboration-view.svelte + its test — it does not touch the store. So the rebase drops the stale S1/S3 base and replays just the S4 UI on top of the guarded store; no hand-fix needed.

Epic order: #1473 (S1) → #1474 (S3) → #1475 (S4), rebasing each onto main as parents land. (CI: no checks reported yet.)