P5: OSS readiness — docs site, contributor onboarding, e2e harness

P5-01 — Documentation site under docs/book/ rendered with mdBook
(downloaded via Makefile, same static-binary pattern as Tailwind).
Structured chapters: getting started, concepts, operations,
security, reference. `make docs` / `make docs-watch`. Generated
output gitignored.

P5-02 — CONTRIBUTING.md rewritten from placeholder to a full
guide. CODE_OF_CONDUCT.md adapted from Contributor Covenant for a
single-maintainer project. .gitea/issue_template/{bug,feature}.md
and PULL_REQUEST_TEMPLATE.md.

P5-04 — Six README screenshots captured live from a fresh server
bootstrap (login, empty dashboard, add-host, alerts, settings,
audit log). README rewritten to centre the screenshot grid and
link out to the docs site.

P5-05 — SECURITY.md with disclosure policy (3-day ack, 30-day
default window), scope in/out, threat-model summary, operator
hardening checklist. Mirrored as a docs-site chapter.

P5-06 — End-to-end test harness. e2e/compose.e2e.yml brings up
server + sibling Linux agent (alpine + restic) + restic/rest-server.
Agent uses announce-and-approve so Playwright can drive the full
operator flow: bootstrap → login → accept pending → backup →
verify terminal status. Second spec scrapes /metrics to assert
the P6-04 endpoint surface. .gitea/workflows/e2e.yml runs on every
PR; local how-to in docs/e2e.md.

docs/book/src/intro.md

@@ -0,0 +1,86 @@
+# restic-manager
+
+restic-manager is a self-hosted, browser-based, single-pane-of-glass
+for managing [restic](https://restic.net) backups across a fleet of
+Linux and Windows endpoints. It's designed for **small fleets** —
+the original target was twelve endpoints — and **one operator**.
+
+## What it does
+
+- Centralised view of every endpoint's last backup, repo size,
+  snapshot count, and recent jobs.
+- Trigger any restic operation remotely (`backup`, `forget`, `prune`,
+  `check`, `unlock`, `snapshots`, `stats`, `diff`, `restore`).
+- Per-host backup schedules with source groups (named bundles of
+  paths + retention policy).
+- Live job log streamed to the browser; downloadable as text or NDJSON.
+- Restore wizard with snapshot tree browse + path selection.
+- Repo-level health surfacing (size, raw size, last-check, lock
+  state) plus a 30/90-day size trend.
+- Alerting over webhook, ntfy, or SMTP.
+- Cross-platform agent (Linux + Windows).
+- Append-only-credential-friendly with a separate admin credential
+  for forget/prune.
+
+## What it isn't
+
+- **Not a SaaS.** Single-instance, single-tenant, by design.
+- **Not a replacement for restic** — it's a control plane. The agent
+  shells out to a real `restic` binary.
+- **Not highly available.** SQLite, single process; if you need
+  HA backups, you're shopping in the wrong aisle.
+- **Not a multi-protocol backup tool.** restic only.
+
+## How it fits together
+
+```
+┌──────────────────────────────────────────────┐
+│  Server (control plane, Docker)              │
+│   - REST + WebSocket API                     │
+│   - SQLite store                             │
+│   - Embedded HTMX UI                         │
+└──────────┬─────────────────────────┬─────────┘
+           │ outbound WS              │ HTTP(S)
+           │                          │
+┌──────────▼──────────┐    ┌──────────▼─────────┐
+│  Agent (per host)   │    │  Browser (operator) │
+│   - restic wrapper  │    └─────────────────────┘
+│   - cron for sched. │
+└──────────┬──────────┘
+           │ restic
+┌──────────▼──────────────────────────────────┐
+│  rest-server / S3 / SFTP / local repo       │
+│  (the actual backup data — server never     │
+│   touches it)                               │
+└─────────────────────────────────────────────┘
+```
+
+The control plane is a Go binary that runs in Docker. Each endpoint
+runs a small Go agent that holds an outbound WebSocket to the
+control plane. Backup data flows directly between the agent and the
+restic repository — the control plane never sees a snapshot byte.
+
+## Where to start
+
+- [Installing the server](./getting-started/install.md) walks
+  through the Docker-based reference deployment.
+- [Enrolling your first host](./getting-started/enrolling-hosts.md)
+  covers the install scripts and the announce-and-approve flow.
+- [Architecture](./concepts/architecture.md) is the right read if
+  you want to know why something is the way it is before running
+  the install.
+
+## Project status
+
+Pre-1.0 but feature-complete for the original use case. Phases
+0–4 are landed (MVP, scheduling, restore, RBAC + OIDC); Phase 5
+(this docs site, contributor onboarding, end-to-end CI) is in
+flight. See [`tasks.md`](https://gitea.dcglab.co.uk/steve/restic-manager/src/branch/main/tasks.md)
+for the live roadmap and [`spec.md`](https://gitea.dcglab.co.uk/steve/restic-manager/src/branch/main/spec.md)
+for the canonical design doc.
+
+## License
+
+[PolyForm Noncommercial 1.0.0](https://polyformproject.org/licenses/noncommercial/1.0.0/).
+Personal and community deployments welcome; commercial use
+requires a separate license.