P1 polish: agent-as-root, init-repo flow, rest creds passthrough, UX fixes

Cohesive batch from a smoke-test session against a real rest-server.
Themed bullets:

* Agent runs as root, sandboxed via systemd. CapabilityBoundingSet
  drops to CAP_DAC_READ_SEARCH + restore caps; ProtectSystem=strict
  with ReadWritePaths confined to /etc + /var/lib/restic-manager;
  NoNewPrivileges blocks escalation. Install script no longer
  creates a service user. spec.md §4.2 / §14.1 / §14.3 explain the
  rationale (matches UrBackup / Veeam / Bareos defaults; trying to
  back up "everything" as an unprivileged user creates silent skips
  on /home, /root, /var/lib/* with no upside vs the threat model
  the agent already implies).

* Init-repo end-to-end. New JobKind="init" wired through agent
  runner, restic.Env.RunInit, server dispatcher, and a UI button
  (red "Initialise repo" in the run-now panel). hosts.repo_initialised_at
  flips on init success, on backup success, or on a non-empty
  snapshots.report. The "Run now" / "Init" / "Retry" branching now
  drives both the dashboard host row and the host-detail panel.
  Migrations 0004 (column), 0005 (jobs.kind CHECK widened — using
  the safe create-new-then-rename pattern; first version corrupted
  job_logs.job_id FK), 0006 (cleans up job_logs FK on already-
  affected DBs).

* rest-server creds embedded at exec time only. restic.Env gains
  RepoUsername; mergeRestCreds() builds the user:pass@-prefixed URL
  inside envSlice() and never assigns it back to the struct, so
  nothing slog-able ever sees the cleartext form. RedactURL helper
  for any future surface that needs to log a URL safely. Both
  helpers tested.

* Add-host UX. Repo password is now optional — server mints a
  24-byte URL-safe random one and surfaces it once, alongside an
  htpasswd snippet ("echo PASS | htpasswd -B -i ... USERNAME") so
  the operator pastes one command on the rest-server host and one
  on the endpoint. Result page also links the install snippet at
  /install/install.sh (was /install.sh — 404'd before) and pipes
  to bash (not sh — script uses set -o pipefail and other
  bashisms; on Debian/Ubuntu sh is dash).

* Late-subscriber race in JobHub. A fast-failing job could finish
  (DB write + Broadcast) before the browser's HX-Redirect → page
  load → WS-connect path completed, so the JS sat forever waiting
  on a job.finished that already passed. JobHub split into
  Register + Send + Run; handleJobStream now subscribes first,
  re-fetches the job, and sends a synthetic job.finished if the
  state is already terminal.

* HTMX error visibility. New toast partial listens to
  htmx:responseError and surfaces the response body as a
  bottom-right toast — every server-side validation error now
  becomes visible without per-handler JS wiring. Also handles
  custom rm:toast events for future server-pushed notifications
  via the HX-Trigger header. Themed via existing CSS vars.

* Dashboard rows are now whole-row clickable to host detail
  (CSS card-link pattern: absolute-positioned anchor + .row-action
  z-index restoration so the action button stays clickable).
  "View →" on a running job links to /jobs/<id> rather than
  /hosts/<id> since the row click already covers the host page.

* "Run first" / "Run first backup" → "Run now" everywhere for
  consistency.

* runbook (docs/e2e-smoke.md) updated — live-log streaming step
  now reflects P1-26; mentions the browser-driven Run-now flow.

* _diag/dump-creds — moved out of cmd/ so go build doesn't pick
  it up; .gitignore now excludes /_diag/ entirely.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

deploy/install/install.sh

@@ -2,19 +2,23 @@
 # install.sh — Linux installer for the restic-manager agent.
 #
 # Usage (paste in shell):
-#   curl -fsSL https://restic.lab.example/install.sh | \
-#     sudo RM_SERVER=https://restic.lab.example RM_TOKEN=<one-time-token> sh
+#   curl -fsSL https://restic.lab.example/install/install.sh | \
+#     sudo RM_SERVER=https://restic.lab.example RM_TOKEN=<one-time-token> bash
 #
 # What it does:
 #   1. detects arch (amd64 / arm64)
 #   2. fetches the matching agent binary from the server
-#   3. creates the restic-manager-agent service user
-#   4. lays down /etc/restic-manager/, /var/lib/restic-manager/
-#   5. enrolls (POST /api/agents/enroll) using RM_TOKEN
-#   6. installs the systemd unit, enables, starts
-#   7. surfaces (but does NOT disable) any existing restic timers /
+#   3. lays down /etc/restic-manager/, /var/lib/restic-manager/ (root:root, 0700)
+#   4. enrolls (POST /api/agents/enroll) using RM_TOKEN
+#   5. installs the systemd unit, enables, starts
+#   6. surfaces (but does NOT disable) any existing restic timers /
 #      cron entries so the operator can decide what to do
 #
+# The agent runs as root. See restic-manager-agent.service for the
+# rationale (in short: a fleet-backup tool must read every file on
+# the system; trying to do that unprivileged buys very little
+# security and creates large UX cliffs).
+#
 # Idempotent — safe to re-run; will refuse if already enrolled
 # unless RM_FORCE_REENROLL=1 is set.
 
@@ -25,8 +29,6 @@ set -euo pipefail
 : "${RM_INSTALL_PREFIX:=/usr/local/bin}"
 : "${RM_CONFIG_DIR:=/etc/restic-manager}"
 : "${RM_STATE_DIR:=/var/lib/restic-manager}"
-: "${RM_USER:=restic-manager-agent}"
-: "${RM_GROUP:=restic-manager-agent}"
 : "${RM_FORCE_REENROLL:=0}"
 
 require_root() {
@@ -44,21 +46,9 @@ detect_arch() {
   esac
 }
 
-ensure_user() {
-  if ! getent group "$RM_GROUP" >/dev/null; then
-    groupadd --system "$RM_GROUP"
-  fi
-  if ! getent passwd "$RM_USER" >/dev/null; then
-    useradd --system --gid "$RM_GROUP" \
-      --home-dir "$RM_STATE_DIR" --no-create-home \
-      --shell /usr/sbin/nologin \
-      "$RM_USER"
-  fi
-}
-
 ensure_dirs() {
-  install -d -m 0750 -o "$RM_USER" -g "$RM_GROUP" "$RM_CONFIG_DIR"
-  install -d -m 0750 -o "$RM_USER" -g "$RM_GROUP" "$RM_STATE_DIR"
+  install -d -m 0700 -o root -g root "$RM_CONFIG_DIR"
+  install -d -m 0700 -o root -g root "$RM_STATE_DIR"
 }
 
 detect_existing_schedulers() {
@@ -121,8 +111,7 @@ enroll_agent() {
   fi
 
   echo "==> Enrolling agent with $RM_SERVER"
-  sudo -u "$RM_USER" \
-    "$RM_INSTALL_PREFIX/restic-manager-agent" \
+  "$RM_INSTALL_PREFIX/restic-manager-agent" \
       -config "$cfg" \
       -enroll-server "$RM_SERVER" \
       -enroll-token "$RM_TOKEN"
@@ -142,7 +131,6 @@ install_unit() {
 
 main() {
   require_root
-  ensure_user
   ensure_dirs
   download_agent
   detect_existing_schedulers