KOL feeds: fix dead/blocked sources, drop stale feeds (29→25)

Feed-health pass over KOL_FEEDS:
- raoulpal: stale Substack (last 2024-05) → Real Vision podcast feed
- dampedspring: paywalled (0 entries) → free "Damped Spring 101" Substack
- unchained: Cloudflare 403 → canonical Megaphone podcast feed
- lynalden: Cloudflare 202 → FeedBurner mirror
- glassnode: recovered via httpx http2=True (was 403 on HTTP/1.1)
- browser User-Agent + Accept headers on feed fetch
- removed dead feeds with no active replacement: placeholder,
  dragonfly, niccarter, eugene
- pin h2==4.3.0 (required by http2=True)

All 25 remaining feeds verified fetching real body content; newest
post per feed ≤88d. Bundles in-flight KOL-module work already in the
working tree (kol_x ingest, migration 027, tests).

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

.env.example

@@ -90,3 +90,9 @@ X_DAILY_CAP=40
 X_FOLLOWUP_MINUTES=15
 # Public URL appended to the follow-up tweet (defaults to FRONTEND_URL if empty).
 X_LINK_URL=
+
+# ── X (Twitter) READ — KOL tweet ingestion (kol_x.py) ────────────────────────
+# twitterapi.io managed-scraper key (x-api-key). Reads other people's tweets —
+# unrelated to the OAuth poster creds above. Empty = X ingestion disabled.
+# Get a pay-as-you-go key at twitterapi.io (~$0.15 / 1k tweets).
+TWITTERAPI_IO_KEY=