[feat](trx-frontend-http): rework the page footer

The footer floated in space below the content with no rule to close the
page, its two clusters sat on a text baseline that left the source pill
hanging, and the status hint was a plain line of text a size larger than
the attribution beside it.

Now a hairline closes the page the way .tab-bar opens it, the clusters
centre on one line, and the attribution drops the opacity it stacked on
top of --text-muted, which had put it below a readable contrast ratio.

The status hint becomes a pill with a state dot: green when ready, amber
while a command is in flight, red on connection loss.  The colour comes
from a data-state attribute, so every hint now goes through setPowerHint
instead of assigning textContent directly.  --status-ok carries the
indicator green; .about-status-on picks it up too, which darkens it on
light themes where the old value was barely legible.

Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/frontend/tests/browser-smoke.mjs

@@ -194,6 +194,15 @@ try {
   await page.locator("summary", { hasText: "Audio controls" }).click();
   assert.equal(await page.locator("#rx-audio-btn").count(), 1);
 
+  // The footer status pill colours its dot from data-state, so a hint written
+  // straight to textContent would leave the dot stuck on the previous state.
+  const hint = await page.evaluate(() => {
+    const element = document.getElementById("power-hint");
+    return { state: element.dataset.state, text: element.textContent.trim() };
+  });
+  assert.ok(["ok", "busy", "error"].includes(hint.state), `status pill state is ${hint.state}`);
+  assert.equal(hint.state, "ok", `fixture reports "${hint.text}" but the pill is ${hint.state}`);
+
   const rigPicker = page.locator("#header-rig-switch-select");
   await rigPicker.locator("option").nth(1).waitFor({ state: "attached" });
   await rigPicker.selectOption("rig-b");