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.

resources/commands/expenses/week.lua

@@ -0,0 +1,37 @@
+-- Sum of the last 7 days' expenses (rolling window).
+
+local lang = jarvis.context.language
+local raw_state = jarvis.state.get("entries") or ""
+if raw_state == "" then
+    return jarvis.cmd.not_found(lang == "ru"
+        and "На этой неделе ничего не тратили."
+        or  "Nothing logged this week.")
+end
+
+local now = jarvis.context.time
+local now_ts = os.time({
+    year = now.year, month = now.month, day = now.day,
+    hour = now.hour, min = now.minute, sec = now.second or 0,
+})
+local cutoff = now_ts - 7 * 86400
+
+local total = 0
+local count = 0
+for chunk in raw_state:gmatch("([^|]+)") do
+    local ts, am = chunk:match("^(%d+),([%-%d%.]+),")
+    ts = tonumber(ts); am = tonumber(am)
+    if ts and am and ts >= cutoff then
+        total = total + am
+        count = count + 1
+    end
+end
+
+if total == 0 then
+    return jarvis.cmd.ok(lang == "ru"
+        and "На этой неделе тратами не похваляешься, сэр."
+        or  "Nothing tracked this week, sir.")
+end
+
+return jarvis.cmd.ok(string.format(lang == "ru"
+    and "За неделю %d трат на сумму %.0f."
+    or  "This week: %d expenses totalling %.0f.", count, total))