feat: Phase 1.5 — health prober, Oracle's Memory, off-thread EPG, PWA

Resilience + scale pass on top of the v1 core.

Stream health prober:
- New SSRF-validated /probe endpoint (HEAD -> ranged-GET fallback, 6s timeout,
  5-min TTL cache, concurrency-capped, no-store) + orb_probe_total metrics
- Front-end health.js: lazy bounded-concurrency probing (current + sampled
  channels, not the whole catalog), LIVE/DEGRADED/DEAD scoring, guide skull
  glyph, instant no-signal on zap to a known-dead channel

Oracle's Memory (memory.js):
- Session resurrection (last channel, volume, mute, theater/dim/ambient)
- Exponential-decay per-channel uptime history; pinning; dead-channel auto-skip

Off-thread XMLTV:
- lib/xmltv-parse.js (pure, hand-rolled scanner, no DOMParser/regex backtracking)
  run in epg-worker.js module worker; wired into the iptv-org provider
- Unit-tested in node: entity decode, TZ offsets, 20k programmes off-thread

Service worker / PWA:
- manifest.webmanifest + orb icons; sw.js (cache-first shell + hls.js,
  stale-while-revalidate for JSON-over-relay, never caches streams)
- CSP gains worker-src + manifest-src; relay sends no-store on /relay + /probe
  so the SW is the sole metadata freshness authority; webmanifest MIME fix

Docs: README de-emojified (title only) and reframed as a peer parallel build.

Verified: SSRF probes blocked, legit probe + cache, new headers present,
PWA assets served, parser tests 8/8, JS syntax clean, zero Rust warnings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/epg-worker.js

@@ -0,0 +1,17 @@
+// epg-worker.js — module worker that parses XMLTV off the main thread.
+//
+// Keeps the guide responsive when a 50MB+ EPG feed lands: the expensive parse
+// happens here, the main thread only receives the finished program array.
+// Launched as `new Worker('./epg-worker.js', { type: 'module' })`.
+
+import { parseXmltv } from './lib/xmltv-parse.js';
+
+self.onmessage = (e) => {
+  const { id, xml } = e.data || {};
+  try {
+    const programs = parseXmltv(xml);
+    self.postMessage({ id, ok: true, programs });
+  } catch (err) {
+    self.postMessage({ id, ok: false, error: String(err) });
+  }
+};