feat(access): демо-QR — многоразовое приглашение для показа

- invites.max_uses/uses: обычное приглашение — 1 вход, демо-QR — до DEMO_INVITE_MAX_USES (50),
  живёт DEMO_INVITE_TTL_HOURS (3 ч); захват атомарный, UPDATE … WHERE uses < max_uses
- users.guest: вошедшие по демо-QR; «🧹 Отключить гостей демо» отзывает всех и гасит демо-QR
- «👥 Участники»: кнопка «🎤 Демо-QR», гости в списке — 🎟
- миграция 0003 (ADD COLUMN без batch — SQLite не пересоздаёт users); проверена на Postgres
- SPEC A-3a, ADR-017, DEMO.md, .env.example

Refs #55

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

app/bot/routers/members.py

@@ -1,4 +1,4 @@
-"""«👥 Участники» for admins: list, invite by QR, revoke access (SPEC A-1, A-7)."""
+"""«👥 Участники» for admins: list, invite by QR (personal or the demo one, #55), revoke access (SPEC A-1, A-7)."""
 
 from datetime import datetime
 from enum import StrEnum
@@ -21,6 +21,9 @@ class MembersAction(StrEnum):
     ASK_REVOKE = "ask"
     REVOKE = "rev"
     LIST = "list"
+    DEMO_INVITE = "demo"
+    ASK_REVOKE_GUESTS = "askg"
+    REVOKE_GUESTS = "revg"
 
 
 class MembersCb(CallbackData, prefix="mem"):
@@ -38,7 +41,7 @@ def render_members(texts: Texts, members: list[User]) -> tuple[str, InlineKeyboa
     for m in members:
         lines.append(
             t.line.format(
-                icon="👑" if m.role is Role.ADMIN else "👤",
+                icon="👑" if m.role is Role.ADMIN else "🎟" if m.guest else "👤",
                 name=m.full_name,
                 username=f" @{m.username}" if m.username else "",
                 joined=_fmt(m.joined_at, t.never),
@@ -47,6 +50,9 @@ def render_members(texts: Texts, members: list[User]) -> tuple[str, InlineKeyboa
         )
     kb = InlineKeyboardBuilder()
     kb.button(text=t.invite, callback_data=MembersCb(action=MembersAction.INVITE))
+    kb.button(text=t.demo_invite, callback_data=MembersCb(action=MembersAction.DEMO_INVITE))
+    if any(m.guest and m.role is not Role.ADMIN for m in members):
+        kb.button(text=t.revoke_guests, callback_data=MembersCb(action=MembersAction.ASK_REVOKE_GUESTS))
     for m in members:
         if m.role is not Role.ADMIN:
             kb.button(
@@ -81,11 +87,14 @@ def build_router(texts: Texts, access: AccessService) -> Router:
             return
         msg = query.message
         match callback_data.action:
-            case MembersAction.INVITE:
-                invite = await access.create_invite(member.tg_id)
+            case MembersAction.INVITE | MembersAction.DEMO_INVITE:
+                demo = callback_data.action is MembersAction.DEMO_INVITE
+                invite = await access.create_invite(member.tg_id, demo=demo)
                 me = await bot.me()
                 link = invite_link(me.username or "", invite.token)
-                caption = t.invite_caption.format(link=link, expires=invite.expires_at.strftime("%d.%m %H:%M"))
+                caption = (t.demo_invite_caption if demo else t.invite_caption).format(
+                    link=link, expires=invite.expires_at.strftime("%d.%m %H:%M"), max_uses=invite.max_uses
+                )
                 await msg.answer_photo(BufferedInputFile(qr_png(link), "invite.png"), caption=caption)
             case MembersAction.ASK_REVOKE:
                 target = await access.get_member(callback_data.tg_id)
@@ -103,6 +112,15 @@ def build_router(texts: Texts, access: AccessService) -> Router:
                 text, kb_markup = render_members(texts, await access.list_members())
                 note = t.revoked.format(name=name) if ok else t.not_revoked
                 await msg.edit_text(f"{note}\n\n{text}", reply_markup=kb_markup)
+            case MembersAction.ASK_REVOKE_GUESTS:
+                kb = InlineKeyboardBuilder()
+                kb.button(text=t.confirm_yes, callback_data=MembersCb(action=MembersAction.REVOKE_GUESTS))
+                kb.button(text=t.confirm_no, callback_data=MembersCb(action=MembersAction.LIST))
+                await msg.edit_text(t.confirm_guests, reply_markup=kb.as_markup())
+            case MembersAction.REVOKE_GUESTS:
+                count = await access.revoke_guests()
+                text, kb_markup = render_members(texts, await access.list_members())
+                await msg.edit_text(f"{t.guests_revoked.format(count=count)}\n\n{text}", reply_markup=kb_markup)
             case MembersAction.LIST:
                 text, kb_markup = render_members(texts, await access.list_members())
                 await msg.edit_text(text, reply_markup=kb_markup)