fix(auth): mount auth router + rename __init__ to router.py

P1.1 — Implement real ai_router.chat_completion / stream_chat_completion
using Ollama Cloud primary + OpenRouter fallback. Fixes AttributeError on
/api/v1/chat and /api/v1/wallet-clusters.

P1.2 — Fix broken RAG call paths: telegram bot now hits /api/v1/rag/v2/search
then ai_router.chat_completion; unified_wallet_scanner._rag_enrich uses
async httpx + correct path. Mount app.domains.databus.router.

P1.3 — Implement setup_otel / shutdown_otel in core/tracing.py and create
core/langfuse.py with init_langfuse / flush_langfuse as safe no-ops when
SDK is missing or env vars unset.

P1.4 — Fix Prometheus alert rule metric name drift:
rmi_requests_total -> rmi_http_requests_total (matches metrics.py).

P1.5 — Move dead admin_backend.py (1691 LOC) to app/domains/admin/router.py
and mount it. Admin login endpoint now reachable.

P2.1 — Rename app/domains/auth/__init__.py (507 LOC router file that broke
mypy) -> app/domains/auth/router.py. Mount app.domains.auth.router so
/register, /login, /wallet/*, /user/me, /2fa/*, OAuth, Telegram are live.

P2.1b — Add pyotp + qrcode to requirements.txt so 2FA endpoints don't 503.

requirements.txt

@@ -7,6 +7,8 @@ python-telegram-bot>=21.0
 supabase>=2.0.0
 python-jose[cryptography]>=3.3.0
 python-multipart>=0.0.17
+pyotp>=2.9.0
+qrcode>=7.4.0
 aiohttp>=3.11.0
 feedparser>=6.0.11
 websockets>=13.0