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.

e2e/agent-entrypoint.sh

@@ -0,0 +1,27 @@
+#!/bin/sh
+# Entrypoint for the e2e agent container.
+#
+# Three states:
+#   1. Already enrolled (agent.yaml has a bearer): run the agent.
+#   2. Token supplied via $RM_ENROL_TOKEN: enrol then run.
+#   3. Otherwise: announce against $RM_SERVER and wait for an admin to
+#      accept us. The announce flow blocks until accepted, then drops
+#      straight into the normal run loop, so this is the test-friendly
+#      path.
+set -eu
+
+CFG="${RM_AGENT_CONFIG:-/etc/restic-manager/agent.yaml}"
+SERVER="${RM_SERVER:?set RM_SERVER}"
+
+if [ -f "$CFG" ] && grep -q '^agent_token:' "$CFG"; then
+    exec restic-manager-agent -config "$CFG"
+fi
+
+if [ -n "${RM_ENROL_TOKEN:-}" ]; then
+    exec restic-manager-agent -config "$CFG" \
+        -enroll-server "$SERVER" \
+        -enroll-token "$RM_ENROL_TOKEN"
+fi
+
+# Announce-and-approve: blocks until an admin accepts, then runs.
+exec restic-manager-agent -config "$CFG" -enroll-server "$SERVER"