fix(usage): check dynamic env and add errors=replace in _token_spy_api_key in usage.py

[vaibhavsrv]

Problem

In ods/extensions/services/dashboard-api/routers/usage.py, _token_spy_api_key() checks module-level TOKEN_SPY_API_KEY, which is evaluated once at import time. If TOKEN_SPY_API_KEY is updated dynamically in os.environ post-import, _token_spy_api_key() returned stale key values. Additionally, reading TOKEN_SPY_KEY_FILE used read_text(encoding="utf-8") without errors="replace" or catching ValueError, causing uncaught decode crashes if key files contained non-standard byte sequences.

Fix

Update _token_spy_api_key() in usage.py to evaluate os.environ.get("TOKEN_SPY_API_KEY") dynamically, pass errors="replace" to read_text(), and catch (OSError, UnicodeError, ValueError).

Verification

Verified syntax with python3 -m py_compile ods/extensions/services/dashboard-api/routers/usage.py. git diff --check passed cleanly.