Bounded buffer with drop policy

DecisionLogPlugin.DecisionLogs buffers events in a ConcurrentLinkedQueue with a soft size check (bufferLimit, default 10000) that triggers a flush only after the threshold is crossed. If uploads are slow or stuck, the buffer can grow without bound — sustained load with a failing service eventually OOMs the process.

• Add a hard cap on the in-memory buffer (configurable, separate from the flush threshold).
• When the cap is reached, drop the oldest or newest event per a configured policy (default: drop oldest, log a warning, increment a decision_logs_dropped counter once the metrics issue lands).
• Tests: sustained writes with a stuck flush stop growing memory and surface the drops.
• Coordinates with the retry/backoff issue (a stuck upstream is exactly the case this guards).

Start in DecisionLogPlugin.DecisionLogs and trace the existing bufferLimit flush path and configuration. Add a separate hard cap and configurable oldest/newest drop policy, then test sustained writes with a stuck flush to verify bounded growth and surfaced drops; coordinate the decision_logs_dropped metric with the metrics issue.