testing: bootstrap UI, agent reliability, NS-01..04 + alert username

Smoothes the rough edges that came up exercising a live deployment.

First-run bootstrap UI: /bootstrap renders a username + password form
that uses the in-memory token directly (operator no longer copies it
out of the log); /login redirects there while bootstrap is available.

Agent reliability: failJob synthetic envelopes so command.run early
returns no longer hang the server-side job; runtime probe of restic
restore --help drives --no-ownership instead of version sniffing
(0.18.x had it removed). Server unit re-shaped: ProtectSystem=full
plus ReadWritePaths=/etc/restic-manager, no ProtectHome — restore
can now write anywhere a user might want.

Restore wizard: default target is /root/rm-restore/<job-id>/ with
clearer help text. Re-init confirm input uses .field (was .input,
which doesn't exist — text was invisible).

NS-01 host delete: store DeleteHost, admin-band /hosts/{id}/delete
with hostname-confirm danger zone, audit, FK cascade, live WS close.

NS-02 enrollment-token recovery: outstanding-tokens panel on
/hosts/new, regenerate (preserves attachments) and revoke handlers
+ audit, store-level ListOutstandingEnrollmentTokens and
DeleteEnrollmentToken.

NS-03 repo init / probe surface: migration 0020 adds
hosts.repo_status + repo_status_error; WS handler projects every
init job's outcome onto the host row (idempotent already-initialised
collapses to ready); creds-save resets status and dispatches a fresh
probe; /hosts/{id}/repo/probe retry endpoint with banner.

NS-04 dashboard live + sort + filter: query-string filter
(q/status/repo_status/tag/sort/dir), 5s htmx live poll mirroring the
alerts pattern with a localStorage live toggle, sortable column
headers, filter row + clear.

Alerts page: ack'd-by line resolves user_id ULID to username.

Compose.yaml ignored — host-specific.

internal/restic/runner.go

@@ -15,6 +15,26 @@ import (
 	"time"
 )
 
+// SupportsRestoreNoOwnership probes the running restic for the
+// `--no-ownership` flag on the `restore` subcommand. Some restic
+// builds (≥ 0.17 in theory; observed missing on a downstream 0.18.1)
+// do not expose it, so we ask the binary directly rather than
+// inferring from the version string. Empty `bin` or any failure to
+// run the help command returns false — the caller stays on the
+// conservative path of not adding the flag.
+func SupportsRestoreNoOwnership(ctx context.Context, bin string) bool {
+	if bin == "" {
+		return false
+	}
+	probeCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
+	defer cancel()
+	out, err := exec.CommandContext(probeCtx, bin, "restore", "--help").CombinedOutput()
+	if err != nil {
+		return false
+	}
+	return strings.Contains(string(out), "--no-ownership")
+}
+
 // Locate resolves the path to the restic binary. Honour an explicit
 // override if provided, else fall back to PATH.
 func Locate(override string) (string, error) {
@@ -49,6 +69,15 @@ type Env struct {
 	ExtraEnv     map[string]string // any other RESTIC_* / passthrough
 	WorkDir      string            // CWD; default = current
 
+	// SupportsRestoreNoOwnership records whether the running restic's
+	// `restore --help` advertises the --no-ownership flag. The flag was
+	// added in 0.17, but at least one downstream build of 0.18.1 still
+	// rejects it ("unknown flag: --no-ownership") — version sniffing
+	// proved unreliable, so the agent now probes for the actual flag at
+	// startup (see internal/restic.SupportsRestoreNoOwnership) and
+	// passes the resulting boolean down here.
+	SupportsRestoreNoOwnership bool
+
 	// Bandwidth caps in KB/s. <=0 means "no cap" (omit the flag).
 	// Emitted as restic global flags --limit-upload / --limit-download
 	// before the subcommand on every invocation.
@@ -507,12 +536,14 @@ func pumpPlain(r io.Reader, stream string, handle LineHandler) error {
 // on one or the other for its cache dir; without it the command
 // fails before ever talking to the repo.
 //
-// Default to /var/lib/restic-manager — that's in the systemd unit's
-// ReadWritePaths and survives ProtectHome=read-only. We do NOT fall
-// back to the parent's HOME env var: the agent runs as root with
-// HOME=/root, but ProtectHome makes /root read-only, so restic's
-// `mkdir /root/.cache/restic` fails. ExtraEnv overrides win for
-// callers that explicitly want a different cache location.
+// Default to /var/lib/restic-manager. The unit no longer pins
+// ProtectHome=read-only (a backup tool needs to restore anywhere),
+// but the explicit HOME stays for two reasons: the parent's HOME
+// can be unset under unusual init shapes, and pinning the cache
+// under a known agent-owned dir keeps restic's metadata isolated
+// from the actual operator home dirs that the agent can now write
+// to. ExtraEnv overrides win for callers that want a different
+// cache location.
 func (e Env) envSlice() []string {
 	home := "/var/lib/restic-manager"
 	if h, ok := e.ExtraEnv["HOME"]; ok && h != "" {