P1 polish: Host.default_paths interim + restic env hygiene + job_id JS quoting

Two fixes that close the loop on dashboard run-now and harden the
agent's restic invocation.

Default paths (interim until P2-01 schedules):
  - 0003 migration adds default_paths TEXT NOT NULL DEFAULT '[]'
    to hosts and to enrollment_tokens.
  - Operator types paths in the Add-host form (textarea, one per
    line). They ride on the enrol_token row alongside the
    encrypted creds (paths aren't secret — plain JSON column).
  - On consume, ConsumeEnrollmentToken still just burns the token;
    the new GetEnrollmentTokenAttachments returns both the
    re-bindable creds and the path list in one round trip, the
    handler transfers them onto the new host row inside CreateHost.
  - The dashboard's Run-now and host-detail's "Run backup now"
    button now read Host.DefaultPaths and pass them to dispatchJob.
    A host with no default paths returns 400 with a friendly
    "no paths set" message instead of dispatching a doomed
    `restic backup` with no positional args.
  - Doc comments explicitly call this out as a Phase 1 interim —
    schedules supersede.

Restic env hygiene:
  - envSlice() previously omitted HOME / XDG_CACHE_HOME, which
    bit the smoke runs whenever the agent was launched outside
    systemd (restic refused to start: "neither $XDG_CACHE_HOME
    nor $HOME are defined"). Now both are set explicitly: prefer
    Env.ExtraEnv overrides, fall back to the agent process's own
    HOME, and finally to /var/lib/restic-manager.
  - Comment makes the env policy explicit: parent's RESTIC_* /
    AWS_* / B2_* env is filtered out by design — control-plane
    is the unambiguous source of truth.

JS bug fix in the live log page:
  - {{$job.ID | printf "%q"}} produced a literal-quoted JS string,
    which then went into the WS URL as ".../jobs/"<ID>"/stream"
    → 404. Switched to '{{$job.ID}}' inside the literal so
    html/template's auto-escape does the right thing. Verified
    end-to-end: dashboard "Run now" → live progress + log lines
    arrive over the WS → succeeded pill renders.

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

internal/server/http/ui_handlers.go

@@ -159,7 +159,26 @@ func (s *Server) handleUIRunBackup(w stdhttp.ResponseWriter, r *stdhttp.Request)
 		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
 		return
 	}
-	res, status, code, msg := s.dispatchJob(r.Context(), storeUser, hostID, api.JobBackup, nil)
+	host, err := s.deps.Store.GetHost(r.Context(), hostID)
+	if err != nil {
+		if errors.Is(err, store.ErrNotFound) {
+			stdhttp.NotFound(w, r)
+			return
+		}
+		stdhttp.Error(w, "internal", stdhttp.StatusInternalServerError)
+		return
+	}
+	if len(host.DefaultPaths) == 0 {
+		// Tell the user with HX-Redirect via a friendly toast — for
+		// now, just an HTTP error: HTMX surfaces the response body
+		// to the operator's console, and a future toast component
+		// will lift it into the UI.
+		stdhttp.Error(w,
+			"this host has no default backup paths set — edit the host or wait for schedules (P2)",
+			stdhttp.StatusBadRequest)
+		return
+	}
+	res, status, code, msg := s.dispatchJob(r.Context(), storeUser, hostID, api.JobBackup, host.DefaultPaths)
 	if code != "" {
 		stdhttp.Error(w, msg, status)
 		return
@@ -188,6 +207,9 @@ type addHostPage struct {
 	Tags         string
 	RepoURL      string
 	RepoUsername string
+	// Paths is the textarea-as-typed default-paths input. One path
+	// per line, blanks ignored.
+	Paths        string
 
 	// Server URL the operator should paste into the install
 	// command. Resolved from RM_BASE_URL falling back to the
@@ -235,6 +257,7 @@ func (s *Server) handleUIAddHostPost(w stdhttp.ResponseWriter, r *stdhttp.Reques
 		Tags:         strings.TrimSpace(r.PostForm.Get("tags")),
 		RepoURL:      strings.TrimSpace(r.PostForm.Get("repo_url")),
 		RepoUsername: strings.TrimSpace(r.PostForm.Get("repo_username")),
+		Paths:        r.PostForm.Get("paths"),
 		ServerURL:    s.publicURL(r),
 	}
 	repoPassword := r.PostForm.Get("repo_password")
@@ -245,8 +268,10 @@ func (s *Server) handleUIAddHostPost(w stdhttp.ResponseWriter, r *stdhttp.Reques
 		page.Error = "Repo URL and password are both required so the agent can back up the moment it comes online."
 	}
 
+	defaultPaths := splitPaths(page.Paths)
+
 	if page.Error == "" {
-		token, expires, err := s.mintEnrollmentToken(r.Context(), page.RepoURL, page.RepoUsername, repoPassword)
+		token, expires, err := s.mintEnrollmentToken(r.Context(), page.RepoURL, page.RepoUsername, repoPassword, defaultPaths)
 		switch err {
 		case nil:
 			page.Token = token
@@ -330,6 +355,19 @@ func (s *Server) handleUIHostDetail(w stdhttp.ResponseWriter, r *stdhttp.Request
 	}
 }
 
+// splitPaths parses the textarea content into a clean []string —
+// one path per line, leading/trailing whitespace trimmed, blanks
+// dropped.
+func splitPaths(s string) []string {
+	out := []string{}
+	for _, line := range strings.Split(s, "\n") {
+		if p := strings.TrimSpace(line); p != "" {
+			out = append(out, p)
+		}
+	}
+	return out
+}
+
 // publicURL is what the operator should paste into the install
 // command. Prefers RM_BASE_URL (set by the operator's reverse
 // proxy config) and falls back to scheme + Host of the inbound