feat: initialize events app with calendars, slots, tickets, and internal API

Extract events/calendar functionality into standalone microservice:
- app.py and events_api.py from apps/events/
- Calendar blueprints (calendars, calendar, calendar_entries, calendar_entry, day, slots, slot, ticket_types, ticket_type)
- Templates for all calendar/event views including admin
- Dockerfile (APP_MODULE=app:app, IMAGE=events)
- entrypoint.sh (no Alembic - migrations managed by blog app)
- Gitea CI workflow for build and deploy

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

bp/calendar_entry/services/ticket_operations.py

@@ -0,0 +1,87 @@
+from __future__ import annotations
+
+from typing import Optional
+from decimal import Decimal
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from models.calendars import CalendarEntry
+
+
+async def update_ticket_config(
+    session: AsyncSession,
+    entry_id: int,
+    ticket_price: Optional[Decimal],
+    ticket_count: Optional[int],
+) -> tuple[bool, Optional[str]]:
+    """
+    Update ticket configuration for a calendar entry.
+
+    Args:
+        session: Database session
+        entry_id: Calendar entry ID
+        ticket_price: Price per ticket (None = no tickets)
+        ticket_count: Total available tickets (None = unlimited)
+
+    Returns:
+        (success, error_message)
+    """
+    # Get the entry
+    entry = await session.scalar(
+        select(CalendarEntry).where(
+            CalendarEntry.id == entry_id,
+            CalendarEntry.deleted_at.is_(None)
+        )
+    )
+
+    if not entry:
+        return False, "Calendar entry not found"
+
+    # Validate inputs
+    if ticket_price is not None and ticket_price < 0:
+        return False, "Ticket price cannot be negative"
+
+    if ticket_count is not None and ticket_count < 0:
+        return False, "Ticket count cannot be negative"
+
+    # Update ticket configuration
+    entry.ticket_price = ticket_price
+    entry.ticket_count = ticket_count
+
+    return True, None
+
+
+async def get_available_tickets(
+    session: AsyncSession,
+    entry_id: int,
+) -> tuple[Optional[int], Optional[str]]:
+    """
+    Get the number of available tickets for a calendar entry.
+
+    Returns:
+        (available_count, error_message)
+        - available_count is None if unlimited tickets
+        - available_count is the remaining count if limited
+    """
+    entry = await session.scalar(
+        select(CalendarEntry).where(
+            CalendarEntry.id == entry_id,
+            CalendarEntry.deleted_at.is_(None)
+        )
+    )
+
+    if not entry:
+        return None, "Calendar entry not found"
+
+    # If no ticket configuration, return None (unlimited)
+    if entry.ticket_price is None:
+        return None, None
+
+    # If ticket_count is None, unlimited tickets
+    if entry.ticket_count is None:
+        return None, None
+
+    # TODO: Subtract booked tickets when ticket booking is implemented
+    # For now, just return the total count
+    return entry.ticket_count, None