Fixed metrics pages showing "No token usage data yet" despite completed researches (#4457). LLM calls whose provider returns no token usage data (OpenAI-compatible servers that omit `usage` on streamed responses, proxies that strip it, Ollama omitting `prompt_eval_count` for fully-cached prompts) were silently skipped, leaving every metrics panel empty; they are now recorded with zero token counts plus a warning log, so call counts, models, phases and response times still appear. Added an opt-in `llm.openai_endpoint.stream_usage` setting that requests usage stats on streamed responses (`stream_options.include_usage`) for servers that support it (LM Studio 0.3.18+, llama.cpp, vLLM, OpenRouter) — off by default because some gateways reject the parameter with a 400. Also fixed background-thread token writes not updating the `ModelUsage` aggregate, and several /metrics panels ignoring the selected time period: the research count, plus the ratings, link and strategy analytics, fell back to a fixed 30-day (or all-time) window when "3 months" or "1 year" was chosen, because the period vocabularies were inconsistent. All metrics endpoints now share one period map.
