[feat](trx-frontend-http): display RDS PS name overlay on overview strip

When a WFM/SDR spectrum stream carries RDS data, show the Program
Service name (8-char station name) centered on the visible waveform
area in DSEG14 monospace — the same font as the frequency display.

- Add #rds-ps-overlay div inside .overview-strip (pointer-events: none,
  z-index: 2, absolutely positioned at the center of the visible canvas)
- updateRdsPsOverlay(rds) shows/hides and updates text on every spectrum
  frame; trims trailing spaces common in RDS PS strings
- Overlay cleared on spectrum disconnect / null frame
- text-shadow uses CSS color-mix against --bg for legibility across all
  style/theme combinations

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Stan Grams <sjg@haxx.space>

src/trx-client/trx-frontend/trx-frontend-http/assets/web/style.css

@@ -411,6 +411,22 @@ small { color: var(--text-muted); }
   position: relative;
   z-index: 1;
 }
+#rds-ps-overlay {
+  display: none;
+  position: absolute;
+  top: calc(var(--header-waterfall-overlap) + clamp(4.2rem, 11vh, 6.25rem) / 2);
+  left: 50%;
+  transform: translate(-50%, -50%);
+  z-index: 2;
+  pointer-events: none;
+  font-family: 'DSEG14 Classic', monospace;
+  font-size: 2rem;
+  letter-spacing: 0.05em;
+  color: var(--text-heading);
+  opacity: 0.88;
+  text-shadow: 0 1px 8px color-mix(in srgb, var(--bg) 60%, transparent);
+  white-space: nowrap;
+}
 .overview-toolbar {
   display: flex;
   align-items: center;