Architecture diagram: current main, timeline histogram

- Title without the commit hash (the hand-drawn font turned "32593b9" into
  "3259369"); the subtitle dates the diagram instead.
- New Histogram (histogram.go) box: API -> histogram -> VictoriaLogs (stats).
- Query mentions the from/to range (zoom); the web UI mentions the
  timeline, columns and live view.
- Multi-segment arrows drawn straight, routed between the containers.
- PNG regenerated from the .excalidraw source (Excalidraw 0.18 renderer).
- README: histogram.go in the Search flow.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

README.md

@@ -18,7 +18,8 @@ devices ──514 udp/tcp──▶ logstream (Go) ──HTTP batches──▶ Vi
   on IP hosts), then the `Store` queue, which sends them in batches to VictoriaLogs.
 - **Live view**: `sink()` also publishes each message to the `Hub`, which streams it to the
   browsers over SSE.
-- **Search**: the HTTP API turns the UI filters into LogsQL queries sent to VictoriaLogs.
+- **Search**: the HTTP API turns the UI filters into LogsQL queries sent to VictoriaLogs;
+  `histogram.go` computes the timeline intervals (division, time zone, count per severity).
 - **State**: tags and source settings live in `/data` (`logstream-data` volume); the logs
   themselves in the `vlogs-data` volume.