Fix Neo4j tag filter returning all events instead of filtering (v0.49.2)

- Change OPTIONAL MATCH to EXISTS subquery for tag filtering in Neo4j
  - OPTIONAL MATCH returned rows even when tags didn't match (NULL values)
  - EXISTS subquery correctly requires matching tags to exist
- Strip "#" prefix from filter tag types before matching
  - Filters use "#d", "#p", "#e" but events store tags without prefix
- Add trace-level logging for Neo4j query debugging
- Add comprehensive tests for Neo4j query builder
- Clean up temporary debug logging from handle-req.go

Files modified:
- pkg/neo4j/query-events.go: Fix tag filtering with EXISTS subquery
- pkg/neo4j/query-events_test.go: Add query builder tests
- app/handle-req.go: Remove debug logging
- pkg/version/version: Bump to v0.49.2

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/handle-req.go

@@ -34,7 +34,6 @@ import (
 
 func (l *Listener) HandleReq(msg []byte) (err error) {
 	log.D.F("handling REQ: %s", msg)
-	log.T.F("HandleReq: START processing from %s", l.remote)
 	// var rem []byte
 	env := reqenvelope.New()
 	if _, err = env.Unmarshal(msg); chk.E(err) {