Flush loop: swallowed errors fire forever without backoff

[AndresL230]

Summary

recost/_init.py:194-195 catches every exception in the flush loop and continues firing every flush_interval_ms. A deterministic bug (malformed metric, transport never reachable) silently re-fires forever, logging every cycle.

Fix

Track consecutive failures; after N (e.g. 5), back off exponentially up to a ceiling, and surface via on_error.

Files

• recost/_init.py
• tests/test_init.py

Priority

P2 — log spam under sustained failure; not data-loss but a poor operator experience.