Add archive relay query augmentation and access-based GC (v0.45.0)

- Add async archive relay querying (local results immediate, archives in background)
- Add query caching with filter normalization to avoid repeated requests
- Add session-deduplicated access tracking for events
- Add continuous garbage collection based on access patterns
- Auto-detect storage limit (80% of filesystem) when ORLY_MAX_STORAGE_BYTES=0
- Support NIP-50 search queries to archive relays

New environment variables:
- ORLY_ARCHIVE_ENABLED: Enable archive relay query augmentation
- ORLY_ARCHIVE_RELAYS: Comma-separated archive relay URLs
- ORLY_ARCHIVE_TIMEOUT_SEC: Archive query timeout
- ORLY_ARCHIVE_CACHE_TTL_HRS: Query deduplication window
- ORLY_GC_ENABLED: Enable access-based garbage collection
- ORLY_MAX_STORAGE_BYTES: Max storage (0=auto 80%)
- ORLY_GC_INTERVAL_SEC: GC check interval
- ORLY_GC_BATCH_SIZE: Events per GC cycle

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

pkg/neo4j/access_tracking.go

@@ -0,0 +1,94 @@
+package neo4j
+
+import (
+	"context"
+	"fmt"
+	"time"
+)
+
+// RecordEventAccess updates access tracking for an event in Neo4j.
+// This creates or updates an AccessTrack node for the event.
+func (n *N) RecordEventAccess(serial uint64, connectionID string) error {
+	cypher := `
+MERGE (a:AccessTrack {serial: $serial})
+ON CREATE SET a.lastAccess = $now, a.count = 1
+ON MATCH SET a.lastAccess = $now, a.count = a.count + 1`
+
+	params := map[string]any{
+		"serial": int64(serial), // Neo4j uses int64
+		"now":    time.Now().Unix(),
+	}
+
+	_, err := n.ExecuteWrite(context.Background(), cypher, params)
+	if err != nil {
+		return fmt.Errorf("failed to record event access: %w", err)
+	}
+
+	return nil
+}
+
+// GetEventAccessInfo returns access information for an event.
+func (n *N) GetEventAccessInfo(serial uint64) (lastAccess int64, accessCount uint32, err error) {
+	cypher := "MATCH (a:AccessTrack {serial: $serial}) RETURN a.lastAccess AS lastAccess, a.count AS count"
+	params := map[string]any{"serial": int64(serial)}
+
+	result, err := n.ExecuteRead(context.Background(), cypher, params)
+	if err != nil {
+		return 0, 0, fmt.Errorf("failed to get event access info: %w", err)
+	}
+
+	ctx := context.Background()
+	if result.Next(ctx) {
+		record := result.Record()
+		if record != nil {
+			if la, found := record.Get("lastAccess"); found {
+				if v, ok := la.(int64); ok {
+					lastAccess = v
+				}
+			}
+			if c, found := record.Get("count"); found {
+				if v, ok := c.(int64); ok {
+					accessCount = uint32(v)
+				}
+			}
+		}
+	}
+
+	return lastAccess, accessCount, nil
+}
+
+// GetLeastAccessedEvents returns event serials sorted by coldness.
+func (n *N) GetLeastAccessedEvents(limit int, minAgeSec int64) (serials []uint64, err error) {
+	cutoffTime := time.Now().Unix() - minAgeSec
+
+	cypher := `
+MATCH (a:AccessTrack)
+WHERE a.lastAccess < $cutoff
+RETURN a.serial AS serial, a.lastAccess AS lastAccess, a.count AS count
+ORDER BY (a.lastAccess + a.count * 3600) ASC
+LIMIT $limit`
+
+	params := map[string]any{
+		"cutoff": cutoffTime,
+		"limit":  limit,
+	}
+
+	result, err := n.ExecuteRead(context.Background(), cypher, params)
+	if err != nil {
+		return nil, fmt.Errorf("failed to get least accessed events: %w", err)
+	}
+
+	ctx := context.Background()
+	for result.Next(ctx) {
+		record := result.Record()
+		if record != nil {
+			if s, found := record.Get("serial"); found {
+				if v, ok := s.(int64); ok {
+					serials = append(serials, uint64(v))
+				}
+			}
+		}
+	}
+
+	return serials, nil
+}