feat: add user_id ticket support and public events endpoint

- Tickets can be created with user_id instead of name/email
- name/email default to empty string in DB (not NULL-safe)
- New endpoints: GET /api/v1/events/public, GET /api/v1/tickets/user/{user_id}
- POST /api/v1/tickets/{event_id} accepts user_id in body
- Migration m007 adds user_id column to tickets table
- CreateTicket validates: either user_id or (name + email) required

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

models.py

@@ -1,7 +1,8 @@
 from datetime import datetime
+from typing import Optional
 
 from fastapi import Query
-from pydantic import BaseModel, EmailStr, Field, validator
+from pydantic import BaseModel, EmailStr, Field, root_validator, validator
 
 
 class PromoCode(BaseModel):
@@ -66,18 +67,29 @@ class TicketExtra(BaseModel):
 
 
 class CreateTicket(BaseModel):
-    name: str
-    email: EmailStr
+    name: Optional[str] = None
+    email: Optional[str] = None
+    user_id: Optional[str] = None
     promo_code: str | None = None
     refund_address: str | None = None
 
+    @root_validator
+    def validate_identifiers(cls, values):
+        user_id = values.get("user_id")
+        name = values.get("name")
+        email = values.get("email")
+        if not user_id and not (name and email):
+            raise ValueError("Either user_id or both name and email must be provided")
+        return values
+
 
 class Ticket(BaseModel):
     id: str
     wallet: str
     event: str
-    name: str
-    email: str
+    name: str = ""
+    email: str = ""
+    user_id: Optional[str] = None
     registered: bool
     paid: bool
     time: datetime