Addresses all three points from community rate-limiting report:
1. Watchlist scans fetched ALL albums then filtered — 262 albums = 27
API calls per artist. Now determines upfront if full discography is
needed: subsequent scans and time-bounded lookbacks use max_pages=1
(1 API call). Only "full discography" global setting fetches all.
2. MIN_API_INTERVAL (350ms) now configurable via spotify.min_api_interval
setting. Users who get rate-limited frequently can increase the delay.
Floor at 100ms to prevent abuse.
3. Retry-After header extraction improved: added diagnostic logging when
headers exist but lack Retry-After key, plus regex fallback to parse
the value from the error message string.
Broque Thomas
4e4f258d25
