Make paywalls systemic + fix ArticleCard reactivity

- ArticleCard: derive safeHref from article.url and reset image-failure state
  when the article changes, so in-place replacements re-evaluate correctly
  (clears the Svelte capture warning; build is warning-free again).
- Downweight paywalled stories below readable ones (stable sort) when composing
  the daily five and in feed results — the brief now leads readable and rarely
  hands over a locked door.
- review_sources gains a 'paywall-heavy' advisory flag (Nature, New Scientist
  flag at 100%); never auto-deactivates.
- New Scientist/Nature kept active but no longer reach the daily five; they
  remain browsable with the label + Replace.
- Tests: brief readability preference + paywall-heavy flag (79 total).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

goodnews/sources.py

@@ -7,6 +7,8 @@ from datetime import datetime, timezone
 from pathlib import Path
 from urllib.parse import urlsplit
 
+from .paywall import is_paywalled
+
 
 def load_sources(path: Path | str) -> list[dict]:
     data = tomllib.loads(Path(path).read_text(encoding="utf-8"))
@@ -183,7 +185,7 @@ def review_sources(
         recent = conn.execute(
             """
             SELECT sc.accepted, sc.cortisol_score, sc.ragebait_score, a.duplicate_of,
-                   COALESCE(a.published_at, a.discovered_at) AS dt
+                   a.canonical_url, COALESCE(a.published_at, a.discovered_at) AS dt
             FROM articles a
             JOIN article_scores sc ON sc.article_id = a.id
             WHERE a.source_id = ?
@@ -220,6 +222,9 @@ def review_sources(
                 avg_rage = sum(r["ragebait_score"] or 0 for r in recent) / n
                 if avg_rage > 3:
                     reasons.append(f"high ragebait (avg {avg_rage:.1f})")
+                paywalled = sum(1 for r in recent if is_paywalled(r["canonical_url"])) / n
+                if paywalled > 0.5:
+                    reasons.append(f"paywall-heavy ({paywalled * 100:.0f}%)")
 
         flag = 1 if reasons else 0
         reason = "; ".join(reasons) if reasons else None