feat: Wave 10 — expense tracker pack (voice-driven)
resources/commands/expenses/ (4 commands):
- expenses.log "потратил 500 на еду" → append entry
- expenses.today "сколько потратил сегодня" → today's total
- expenses.week "сколько на неделе" → 7-day rolling total
- expenses.breakdown "куда ушли деньги" → top-5 categories
Storage: `jarvis.state` (auto-namespaced per-pack JSON). Wire format is
compact "ts1,amount1,cat1|ts2,amount2,cat2" so we don't need a JSON parser
inside Lua.
Phrase parsing:
- Trigger stripped via jarvis.text.strip_trigger.
- First number captured; "12,50" comma decimals accepted.
- Category extracted from "на <слово>" (RU) or "for/on <word>" (EN);
defaults to "разное" / "misc".
Time math:
- Day boundary: local-calendar midnight via os.time({year,month,day,...}).
- Week boundary: rolling 7×86400 seconds.
Pack count: 98 → 99 functional.
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