Add documentation and improve BBolt import memory efficiency (v0.48.8)

- Add README.md table of contents for easier navigation
- Add Curation ACL documentation section to README.md
- Create detailed Curation Mode Guide (docs/CURATION_MODE_GUIDE.md)
- Fix OOM during BBolt index building by closing temp file before build
- Add GC calls before index building to reclaim batch buffer memory
- Improve import-export.go with processJSONLEventsReturningCount
- Add policy-aware import path for sync operations

Files modified:
- README.md: Added TOC and curation ACL documentation
- docs/CURATION_MODE_GUIDE.md: New comprehensive curation mode guide
- pkg/bbolt/import-export.go: Memory-safe import with deferred cleanup
- pkg/bbolt/import-minimal.go: Added GC before index build
- pkg/version/version: Bump to v0.48.8

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

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

pkg/bbolt/import-minimal.go

@@ -62,9 +62,12 @@ func (b *B) BuildIndexes(ctx context.Context) error {
 	log.I.F("bbolt: starting index build...")
 	startTime := time.Now()
 
-	// Process in chunks to avoid OOM
-	// With ~15 indexes per event and ~50 bytes per key, 200k events = ~150MB
-	const chunkSize = 200000
+	// Force GC before starting to reclaim batch buffer memory
+	debug.FreeOSMemory()
+
+	// Process in small chunks to avoid OOM on memory-constrained systems
+	// With ~15 indexes per event and ~50 bytes per key, 50k events = ~37.5MB per chunk
+	const chunkSize = 50000
 
 	var totalEvents int
 	var lastSerial uint64 = 0