feat: ticket purchase flow, QR display, and admin check-in

Ticket purchase:
- tickets blueprint with routes for my tickets list, ticket detail with QR
- Buy tickets form on entry detail page (HTMX-powered)
- Ticket services: create, query, availability checking

Admin check-in:
- ticket_admin blueprint with dashboard, lookup, and check-in routes
- QR scanner/lookup interface with real-time search
- Per-entry ticket list view
- Check-in transitions ticket state to checked_in

Internal API:
- GET /internal/events/tickets endpoint for cross-app queries
- POST /internal/events/tickets/<code>/checkin for programmatic check-in

Template fixes:
- All templates updated: blog.post.calendars.* → calendars.*
- Removed slug=post.slug parameters (standalone events service)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bp/ticket_admin/routes.py

@@ -0,0 +1,166 @@
+"""
+Ticket admin blueprint — check-in interface and ticket management.
+
+Routes:
+  GET  /admin/tickets/              — Ticket dashboard (scan + list)
+  GET  /admin/tickets/entry/<id>/   — Tickets for a specific entry
+  POST /admin/tickets/<code>/checkin — Check in a ticket
+  GET  /admin/tickets/<code>/       — Ticket admin detail
+"""
+from __future__ import annotations
+
+import logging
+
+from quart import (
+    Blueprint, g, request, render_template, make_response, jsonify,
+)
+from sqlalchemy import select, func
+from sqlalchemy.orm import selectinload
+
+from models.calendars import CalendarEntry, Ticket, TicketType
+from suma_browser.app.authz import require_admin
+from suma_browser.app.redis_cacher import clear_cache
+
+from ..tickets.services.tickets import (
+    get_ticket_by_code,
+    get_tickets_for_entry,
+    checkin_ticket,
+)
+
+logger = logging.getLogger(__name__)
+
+
+def register() -> Blueprint:
+    bp = Blueprint("ticket_admin", __name__, url_prefix="/admin/tickets")
+
+    @bp.get("/")
+    @require_admin
+    async def dashboard():
+        """Ticket admin dashboard with QR scanner and recent tickets."""
+        from suma_browser.app.utils.htmx import is_htmx_request
+
+        # Get recent tickets
+        result = await g.s.execute(
+            select(Ticket)
+            .options(
+                selectinload(Ticket.entry).selectinload(CalendarEntry.calendar),
+                selectinload(Ticket.ticket_type),
+            )
+            .order_by(Ticket.created_at.desc())
+            .limit(50)
+        )
+        tickets = result.scalars().all()
+
+        # Stats
+        total = await g.s.scalar(select(func.count(Ticket.id)))
+        confirmed = await g.s.scalar(
+            select(func.count(Ticket.id)).where(Ticket.state == "confirmed")
+        )
+        checked_in = await g.s.scalar(
+            select(func.count(Ticket.id)).where(Ticket.state == "checked_in")
+        )
+        reserved = await g.s.scalar(
+            select(func.count(Ticket.id)).where(Ticket.state == "reserved")
+        )
+
+        stats = {
+            "total": total or 0,
+            "confirmed": confirmed or 0,
+            "checked_in": checked_in or 0,
+            "reserved": reserved or 0,
+        }
+
+        if not is_htmx_request():
+            html = await render_template(
+                "_types/ticket_admin/index.html",
+                tickets=tickets,
+                stats=stats,
+            )
+        else:
+            html = await render_template(
+                "_types/ticket_admin/_main_panel.html",
+                tickets=tickets,
+                stats=stats,
+            )
+
+        return await make_response(html, 200)
+
+    @bp.get("/entry/<int:entry_id>/")
+    @require_admin
+    async def entry_tickets(entry_id: int):
+        """List all tickets for a specific calendar entry."""
+        from suma_browser.app.utils.htmx import is_htmx_request
+
+        entry = await g.s.scalar(
+            select(CalendarEntry)
+            .where(
+                CalendarEntry.id == entry_id,
+                CalendarEntry.deleted_at.is_(None),
+            )
+            .options(selectinload(CalendarEntry.calendar))
+        )
+        if not entry:
+            return await make_response("Entry not found", 404)
+
+        tickets = await get_tickets_for_entry(g.s, entry_id)
+
+        html = await render_template(
+            "_types/ticket_admin/_entry_tickets.html",
+            entry=entry,
+            tickets=tickets,
+        )
+        return await make_response(html, 200)
+
+    @bp.get("/lookup/")
+    @require_admin
+    async def lookup():
+        """Look up a ticket by code (used by scanner)."""
+        code = request.args.get("code", "").strip()
+        if not code:
+            return await make_response(
+                '<div class="text-sm text-stone-500">Enter a ticket code</div>',
+                200,
+            )
+
+        ticket = await get_ticket_by_code(g.s, code)
+        if not ticket:
+            html = await render_template(
+                "_types/ticket_admin/_lookup_result.html",
+                ticket=None,
+                error="Ticket not found",
+            )
+            return await make_response(html, 200)
+
+        html = await render_template(
+            "_types/ticket_admin/_lookup_result.html",
+            ticket=ticket,
+            error=None,
+        )
+        return await make_response(html, 200)
+
+    @bp.post("/<code>/checkin/")
+    @require_admin
+    @clear_cache(tag="calendars", tag_scope="all")
+    async def do_checkin(code: str):
+        """Check in a ticket by its code."""
+        success, error = await checkin_ticket(g.s, code)
+
+        if not success:
+            html = await render_template(
+                "_types/ticket_admin/_checkin_result.html",
+                success=False,
+                error=error,
+                ticket=None,
+            )
+            return await make_response(html, 200)
+
+        ticket = await get_ticket_by_code(g.s, code)
+        html = await render_template(
+            "_types/ticket_admin/_checkin_result.html",
+            success=True,
+            error=None,
+            ticket=ticket,
+        )
+        return await make_response(html, 200)
+
+    return bp