feat(meet-kevin): throttle inter-video LLM calls (30s) to stay under Anthropic RPM

First production run hit Anthropic's per-account rate_limit_error (429) trying
to burn through 16 backfill videos in seconds. The SDK's built-in retry can't
recover because the rate limit window resets slower than the 3 retry attempts.

Added meet_kevin_inter_video_sleep_seconds (default 30s) to PipelineDeps and
main's _process_pending_videos loop. 16 backfill videos now take ~8 min (16 * 30s
sleeps + ~30s per LLM call) instead of bursting into the rate limit.

services/meet_kevin_watcher/config.py

@@ -21,6 +21,7 @@ class MeetKevinWatcherConfig(BaseConfig):
     meet_kevin_llm_model: str = "claude-sonnet-4-5"
     meet_kevin_prompt_version: str = "v1"
     meet_kevin_daily_cost_cap_usd: float = 5.0
+    meet_kevin_inter_video_sleep_seconds: int = 30
 
     # API credentials
     anthropic_oauth_token: str = ""