Empty or degraded Tautulli watch history can mass-delete watched content

[rfsbraz]

Description

Tautulli.get_activity() (app/modules/tautulli.py) returns an empty dict on any empty fetch, with no sanity check. Downstream, an empty activity dict makes find_watched_data return None for every item, which bypasses both last_watched_threshold and the recently-watched protection in check_watched_status (app/media_cleaner.py).

With a common config (watch_status: unwatched, or a bare last_watched_threshold), that turns EVERY item in the library into an actionable deletion candidate - up to max_actions_per_run recently-watched titles get deleted, silently, on a single bad run.

Failure Scenario

Tautulli is reachable but returns empty or partial history: database rebuild in progress, section ID mismatch after a Plex library re-add, auth quietly returning an empty set. Deleterr interprets "no watch data" as "nothing was ever watched" and deletes accordingly. This is the worst failure class for a deletion tool: irreversible, silent, and triggered by a dependency being degraded rather than down.

Proposed Fix

• Treat zero or near-zero activity as suspicious: abort a library's deletions when watch activity is empty, or dramatically below the previous run's count (persist the last count in the state file)
• Distinguish "genuinely empty history" from "fetch returned nothing" and fail safe on the latter
• Log the abort loudly and send a failure notification
• Add regression tests asserting empty activity yields ZERO deletions