Scaffold Phase 0: agent -> Redpanda -> ingest -> ClickHouse -> api -> web

End-to-end log pipeline for Linux hosts, per /docs/architecture.md:

- proto: shared gRPC contract (agent <-> ingest), Go bindings checked in
- agent: Rust, musl-targeted, journald/file sourcing, RFC5424 parser,
  mTLS gRPC client, no required config for the common case
- ingest: Go, single binary with --mode server|consumer|all; gRPC front
  end forwards to Redpanda unchanged, consumer normalizes and
  batch-writes to ClickHouse with at-least-once delivery
- storage: ClickHouse schema + a plain SQL-file migration runner
- api: minimal SELECT-only query endpoint, plain REST (not gRPC+gateway
  yet -- see api/README.md)
- web: SvelteKit static SPA, one query page
- transport: Redpanda compose + topic provisioning
- cli: sentryctl ping stub
- hack/dev-certs: throwaway CA + cert generation for local mTLS
- root docker-compose.yml + docs/phase-0-runbook.md tie it together

Not yet run end-to-end against real Docker/ClickHouse/Redpanda -- see the
runbook's caveats section before relying on this working as-is.

.gitignore

@@ -0,0 +1,21 @@
+# Rust
+agent/target/
+
+# Go build cache (go build ./... without -o doesn't normally leave
+# binaries in-tree, but be defensive)
+/ingest/ingest
+/api/api
+/cli/sentryctl
+
+# Node / SvelteKit (web/ has its own more detailed .gitignore too)
+web/node_modules/
+web/build/
+web/.svelte-kit/
+
+# Dev-only generated secrets
+hack/dev-certs/out/
+
+# OS / editor
+.DS_Store
+Thumbs.db
+*.swp