Add logviewer: web UI for the ClickHouse log store

Single Go binary with embedded Bootstrap 3 + jQuery UI, querying logs.raw
over the ClickHouse HTTP interface as the readonly logreader user. Runs
behind oauth2-proxy; the app does no auth itself. Server-side enforced
time bounds (15m default, 72h max), parameterized queries, raw-SQL WHERE
fragment wrapped with enforced bounds and LIMIT, tail polling with a
clamped cursor, facets, healthz. Woodpecker build/test plus tag-driven
image push to artifactapi docker-internal.

web/embed.go

@@ -0,0 +1,7 @@
+// Package web embeds the UI so the server binary is self-contained.
+package web
+
+import "embed"
+
+//go:embed index.html static
+var FS embed.FS