Monochrome updater glyph; fix oversized dialog header icon

The colored updater icon broke the monochrome system-action set in the
sidebar. Replace it with a new g-update glyph — a down arrow dropping
into an open tray ("get / install updates") — drawn in the same 24×24,
2px round-cap stroke style as the other sidebar glyphs.

- Sidebar Update System row: g-update glyph, currentColor like the rest.
- Update dialog header: same glyph in the green chip, matching the
  rebuild dialog and Systems Operational header treatment.
- Also fixes a latent sizing bug: the previous colored <img> had no CSS
  rule (the .upd-icon rule from the earlier patch never landed), so the
  dialog header icon rendered at the source file's intrinsic 128px. The
  chip markup uses the existing 54px .upd-chip rules.

app/sovran_systemsos_web/static/js/tiles.js

@@ -64,7 +64,7 @@ function renderSidebarSupport(supportServices) {
   sidebarUpdateBtn.className = "sidebar-support-btn";
   sidebarUpdateBtn.id = "sidebar-btn-update";
   sidebarUpdateBtn.innerHTML =
-    '<img class="sidebar-support-icon" src="/static/icons/update.svg" alt="Update" style="width:20px;height:20px;">' +
+    '<span class="sidebar-support-icon"><svg><use href="#g-update"/></svg></span>' +
     '<span class="sidebar-support-text">' +
       '<span class="sidebar-support-title">Update System</span>' +
       '<span class="sidebar-support-hint" id="sidebar-update-hint">Check for updates</span>' +