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/book.toml

@@ -0,0 +1,19 @@
+[book]
+title = "restic-manager"
+description = "Self-hosted control plane for restic backups across a fleet of Linux and Windows endpoints."
+authors = ["Steve Cliff"]
+language = "en-GB"
+multilingual = false
+src = "src"
+
+[output.html]
+default-theme = "ayu"
+preferred-dark-theme = "ayu"
+git-repository-url = "https://gitea.dcglab.co.uk/steve/restic-manager"
+git-repository-icon = "fa-code-fork"
+edit-url-template = "https://gitea.dcglab.co.uk/steve/restic-manager/_edit/main/docs/book/{path}"
+no-section-label = false
+
+[output.html.fold]
+enable = true
+level = 2