feat(meetings): email invites + add external participants by email + share link (batch69)

#4: scheduled meetings can now invite people who aren't on Connect.
- SMTP config (config.js, env-gated: SMTP_HOST/PORT/USER/PASS/FROM/SECURE,
  PUBLIC_BASE_URL) + a small nodemailer wrapper (mailer.js) with a branded
  meeting-invite template carrying the guest join link. No-op until SMTP is set.
- /api/meetings/schedule + /update accept participantEmails; external emails are
  persisted (scheduled_meetings.guest_emails migration) and emailed the guest
  link (plus any invited Connect users with an email on file). Fire-and-forget —
  a mail outage never fails scheduling.
- Meetings list DTO returns `link`; schedule form gains an "Invite by email"
  chip input; each scheduled-meeting card gets a "Copy link" action.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/db.js

@@ -225,6 +225,9 @@ try { db.exec("ALTER TABLE users ADD COLUMN status TEXT NOT NULL DEFAULT 'active
 // their mobile number, so this — not the typed login identifier — is the stable identity key.
 // Provisioning matches on it to keep one Biz Connect account per person (#2 account merge).
 try { db.exec('ALTER TABLE users ADD COLUMN bizgaze_user_id TEXT'); } catch (e) { /* exists */ }
+// External (non-Connect) invitee emails on a scheduled meeting (#4) — JSON array. They get an emailed
+// guest join link instead of an in-app invite.
+try { db.exec('ALTER TABLE scheduled_meetings ADD COLUMN guest_emails TEXT'); } catch (e) { /* exists */ }
 try { db.exec('CREATE INDEX IF NOT EXISTS idx_users_bizgaze_user_id ON users(bizgaze_user_id)'); } catch (e) { /* exists */ }
 // When two accounts merge (#2), the merged-away row is deleted. This records old_id -> survivor so
 // any lingering reference to the old id (a cached contact, an in-flight DM) resolves to the survivor