Cost monitoring, PTT fix, Devon tuning, WEIRD pool expansion, YT thumbnails, LLM SEO, publish ep37

- Add real-time LLM/TTS cost tracking with live status bar display and post-show reports
- Fix PTT bug where Devon suggestion layout shift stopped recording via mouseleave
- Devon: facts-only during calls, full personality between calls
- Double WEIRD topic pool (109→203), bump weight to 14-25%
- Auto-generate YouTube thumbnails with bold hook text in publish pipeline
- LLM SEO: llms.txt, robots.txt for LLM crawlers, structured data, BreadcrumbList schemas
- Publish episode 37

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/services/regulars.py

@@ -53,7 +53,8 @@ class RegularCallerService:
                     location: str, personality_traits: list[str],
                     first_call_summary: str, voice: str = None,
                     stable_seeds: dict = None,
-                    structured_background: dict = None) -> dict:
+                    structured_background: dict = None,
+                    avatar: str = None) -> dict:
         """Promote a first-time caller to regular"""
         # Retire oldest if at cap
         if len(self._regulars) >= MAX_REGULARS:
@@ -72,6 +73,7 @@ class RegularCallerService:
             "voice": voice,
             "stable_seeds": stable_seeds or {},
             "structured_background": structured_background,
+            "avatar": avatar,
             "relationships": {},
             "call_history": [
                 {"summary": first_call_summary, "timestamp": time.time(),