feat: Wave 11 — birthdays tracker pack

resources/commands/birthdays/ (2 commands):
- birthdays.add  "запомни день рождения мама 15 марта" → memory key
  "birthday.мама" = "15.03". Accepts both DD.MM and "DD <month>"
  formats; recognises all 12 RU + 12 EN month names.
- birthdays.next "ближайший день рождения" → reads every "birthday.*"
  memory key, computes days-until each entry (with year wrap), speaks
  the nearest one in human form ("сегодня" / "завтра" / "через N дней").

Storage piggybacks on the existing long-term memory store, so
birthdays survive restart, sync to disk atomically, and don't need a
new persistence layer. Naming convention "birthday.<name>" keeps the
data discoverable in /memory GUI.

Pack count: 99 → 100 functional packs.
Tests: 140 rust, unchanged.

resources/commands/birthdays/add.lua

@@ -0,0 +1,80 @@
+-- Voice "запомни день рождения мама 15 марта" → memory["birthday.мама"]="15.03"
+-- We accept three date formats: "15.03", "15 марта", and "15 march".
+
+local lang = jarvis.context.language
+local raw = (jarvis.context.phrase or ""):lower()
+
+local triggers = {
+    "запомни день рождения", "день рождения у", "добавь день рождения",
+    "запиши день рождения",
+    "remember birthday", "add birthday", "save birthday",
+}
+local rest = jarvis.text.strip_trigger(raw, triggers) or raw
+rest = rest:gsub("^%s+", ""):gsub("%s+$", "")
+
+-- Russian month names → "MM"
+local months_ru = {
+    ["января"]=1, ["январь"]=1,
+    ["февраля"]=2, ["февраль"]=2,
+    ["марта"]=3, ["март"]=3,
+    ["апреля"]=4, ["апрель"]=4,
+    ["мая"]=5, ["май"]=5,
+    ["июня"]=6, ["июнь"]=6,
+    ["июля"]=7, ["июль"]=7,
+    ["августа"]=8, ["август"]=8,
+    ["сентября"]=9, ["сентябрь"]=9,
+    ["октября"]=10, ["октябрь"]=10,
+    ["ноября"]=11, ["ноябрь"]=11,
+    ["декабря"]=12, ["декабрь"]=12,
+}
+local months_en = {
+    january=1, february=2, march=3, april=4, may=5, june=6,
+    july=7, august=8, september=9, october=10, november=11, december=12,
+}
+
+-- Try patterns in order. Each pattern leaves `name` and `date` populated.
+local name, date_str = nil, nil
+
+-- 1. "<name> DD.MM"
+local n, d, m = rest:match("^(.-)%s+(%d?%d)%.(%d?%d)")
+if n and d and m then
+    name = n
+    date_str = string.format("%02d.%02d", tonumber(d), tonumber(m))
+end
+
+-- 2. "<name> DD <month_ru/en>"
+if not name then
+    local n2, d2, mword = rest:match("^(.-)%s+(%d?%d)%s+(%S+)")
+    if n2 and d2 and mword then
+        local m_num = months_ru[mword] or months_en[mword]
+        if m_num then
+            name = n2
+            date_str = string.format("%02d.%02d", tonumber(d2), m_num)
+        end
+    end
+end
+
+if not name or not date_str then
+    return jarvis.cmd.not_found(lang == "ru"
+        and "Скажи в формате 'имя 15 марта' или 'имя 15.03'."
+        or  "Say in the form 'name 15 march' or 'name 15.03'.")
+end
+
+name = name:gsub("^%s+", ""):gsub("%s+$", "")
+if name == "" then
+    return jarvis.cmd.not_found(lang == "ru" and "Чьё именно?" or "Whose?")
+end
+
+-- Strip leading prepositions left from "у мамы" → "мамы"
+name = name:gsub("^у%s+", ""):gsub("^of%s+", ""):gsub("^for%s+", "")
+
+local ok, err = pcall(function()
+    jarvis.memory.remember("birthday." .. name, date_str)
+end)
+if not ok then
+    return jarvis.cmd.error(tostring(err))
+end
+
+return jarvis.cmd.ok(string.format(lang == "ru"
+    and "Запомнил: %s — %s."
+    or  "Got it: %s — %s.", name, date_str))