[BUG] Generic tag-filter (#e, #p, …) subscriptions can return the same event multiple times #693

Describe the bug

In src/repositories/event-repository.ts, when a filter contains a generic tag query, the query builder does a leftJoin onto event_tags and selects events.*:

if (isTagQuery) {
  builder.leftJoin('event_tags', 'events.event_id', 'event_tags.event_id')
    .select('events.*')
}

There is no DISTINCT / GROUP BY on the event id. An event that has multiple rows in event_tags matching the filter criteria (for example a filter of {"#p": ["a", "b"]} matching an event that tags both a and b, or simply an event with several p tags matched by an orWhere) produces one result row per matching tag row. Those rows are streamed straight to the client by SubscribeMessageHandler.fetchAndSend(), so the client receives duplicate EVENT messages for the same event within a single subscription.

To Reproduce

1. Store an event that has two p tags, e.g. ["p","aa..."] and ["p","bb..."].
2. Subscribe with ["REQ","sub",{"#p":["aa...","bb..."]}].
3. The event is delivered twice.

Expected behavior

Each stored event should be delivered at most once per subscription. The join should be de-duplicated (e.g. .distinct('events.event_id') / a GROUP BY, or an EXISTS/whereIn subquery instead of a join).

Screenshots

N/A

System (please complete the following information):

• OS: Linux
• Platform: Docker
• Version: 3.0.0

Logs

N/A - only observable as duplicate EVENT messages received by a subscribed client for the same event id.

Additional context

This is a different root cause from the NIP-01 default-sort-order issue filed separately against this same file - it is about row multiplication from the tag join, not sort direction. Affects any generic tag filter (#e, #p, #g, #r, #d, etc.) where a single event matches more than one event_tags row for the filter's criteria.