feat(email): send booking reminders before event start.

Job process_reminders in subscription_worker; REMINDER_LEAD_HOURS window;
CalenTIQ email + in-app event_reminder; idempotent reminder_sent.
Refs EventHub/EventHubBack#70

src/infra/subscription_worker.erl

@@ -26,6 +26,7 @@ handle_cast(_Msg, State) ->
 handle_info(tick, State) ->
   _ = catch logic_subscription:handle_expired_subscriptions(),
   _ = catch logic_booking:process_timeout_bookings(),
+  _ = catch logic_booking:process_reminders(),
   erlang:send_after(?INTERVAL_MS, self(), tick),
   {noreply, State};
 handle_info(_Info, State) ->

src/logic/logic_booking.erl

@@ -7,7 +7,7 @@
   delete_booking/2,
   list_bookings_admin/0, get_booking_admin/1,
   list_event_bookings/1, list_event_bookings/2,
-  process_timeout_bookings/0, cancel_pending_for_owner/1,
+  process_timeout_bookings/0, process_reminders/0, cancel_pending_for_owner/1,
   cancel_pending_for_calendar/1]).
 
 %%%-------------------------------------------------------------------
@@ -367,6 +367,84 @@ process_timeout_bookings() ->
   lists:foreach(fun(B) -> maybe_timeout(B, NowSec) end, Pending),
   ok.
 
+%%%-------------------------------------------------------------------
+%%% @doc Email + in-app reminder before event start (Back#70).
+%%% Confirmed bookings with reminder_sent=false whose event starts within
+%%% REMINDER_LEAD_HOURS (default 24). Flag set before send (once).
+%%% @end
+%%%-------------------------------------------------------------------
+-spec process_reminders() -> ok.
+process_reminders() ->
+  NowSec = calendar:datetime_to_gregorian_seconds(calendar:universal_time()),
+  LeadSec = reminder_lead_hours() * 3600,
+  Horizon = NowSec + LeadSec,
+  Candidates = mnesia:dirty_match_object(
+    #booking{status = confirmed, reminder_sent = false, _ = '_'}),
+  lists:foreach(fun(B) -> maybe_remind(B, NowSec, Horizon) end, Candidates),
+  ok.
+
+maybe_remind(#booking{id = Id, event_id = EventId, user_id = UserId} = Booking,
+             NowSec, Horizon) ->
+  case core_event:get_by_id(EventId) of
+    {ok, #event{status = active, start_time = Start, title = Title,
+                calendar_id = CalId} = _Event} ->
+      StartSec = calendar:datetime_to_gregorian_seconds(Start),
+      case StartSec > NowSec andalso StartSec =< Horizon of
+        true ->
+          case core_booking:update(Id, [{reminder_sent, true}]) of
+            {ok, _} ->
+              send_reminder(UserId, Title, Start, CalId, EventId),
+              ok;
+            _ ->
+              ok
+          end;
+        false ->
+          ok
+      end;
+    _ ->
+      ok
+  end,
+  Booking.
+
+send_reminder(UserId, Title, Start, CalId, EventId) ->
+  Path = <<"/c/", CalId/binary, "/e/", EventId/binary>>,
+  WhenText = format_when(Start),
+  case core_user:get_by_id(UserId) of
+    {ok, #user{email = Email}} when is_binary(Email), Email =/= <<>> ->
+      _ = logic_email:send_booking_reminder(Email, Title, Start, Path);
+    _ ->
+      ok
+  end,
+  _ = logic_notification:notify_event_reminder(UserId, #{
+    event_id => EventId,
+    calendar_id => CalId,
+    title => Title,
+    start_time => Start,
+    when_text => WhenText
+  }),
+  ok.
+
+format_when({{Y, Mo, D}, {H, Mi, _S}}) ->
+  iolist_to_binary(io_lib:format("~4..0B-~2..0B-~2..0B ~2..0B:~2..0B",
+                                 [Y, Mo, D, H, Mi])).
+
+reminder_lead_hours() ->
+  case application:get_env(eventhub, reminder_lead_hours) of
+    {ok, N} when is_integer(N), N > 0 -> N;
+    _ ->
+      case os:getenv("REMINDER_LEAD_HOURS") of
+        false -> 24;
+        "" -> 24;
+        S ->
+          try list_to_integer(S) of
+            N when N > 0 -> N;
+            _ -> 24
+          catch
+            _:_ -> 24
+          end
+      end
+  end.
+
 maybe_timeout(#booking{id = Id, event_id = EventId, created_at = Created} = Booking, NowSec) ->
   case core_event:get_by_id(EventId) of
     {ok, Event} ->

src/logic/logic_email.erl

@@ -1,5 +1,6 @@
 -module(logic_email).
--export([send_verification_email/2, send_specialist_invite/2, send_password_reset/2]).
+-export([send_verification_email/2, send_specialist_invite/2, send_password_reset/2,
+         send_booking_reminder/4]).
 
 %% SMTP via env (variant A / Back#68):
 %%   SMTP_HOST empty → log-only (local/tests)
@@ -19,6 +20,15 @@ send_specialist_invite(Email, Token) ->
 send_password_reset(Email, Token) ->
   send_kind(reset, Email, abs_url(<<"/reset-password?token=">>, Token)).
 
+%% Reminder before event start (Back#70).
+-spec send_booking_reminder(binary(), binary(), calendar:datetime(), binary()) -> ok.
+send_booking_reminder(Email, EventTitle, StartTime, EventPath) ->
+  Url = abs_path(EventPath),
+  WhenText = format_utc(StartTime),
+  {Subject, Plain, Html} =
+    logic_email_templates:render_reminder(Url, to_bin(EventTitle), WhenText),
+  send(to_bin(Email), Subject, Plain, Html).
+
 send_kind(Kind, To0, Url) ->
   {Subject, Plain, Html} = logic_email_templates:render(Kind, Url),
   send(to_bin(To0), Subject, Plain, Html).
@@ -99,6 +109,18 @@ abs_url(PathPrefix, Token) ->
   TokenB = to_bin(Token),
   <<Base/binary, PathPrefix/binary, TokenB/binary>>.
 
+abs_path(Path0) ->
+  Base = strip_slash(env_bin("PUBLIC_APP_URL", <<"https://stage.calentiq.com">>)),
+  Path = case to_bin(Path0) of
+    <<$/, Rest/binary>> -> <<$/, Rest/binary>>;
+    Rest -> <<$/, Rest/binary>>
+  end,
+  <<Base/binary, Path/binary>>.
+
+format_utc({{Y, Mo, D}, {H, Mi, _S}}) ->
+  iolist_to_binary(io_lib:format("~4..0B-~2..0B-~2..0B ~2..0B:~2..0B",
+                                 [Y, Mo, D, H, Mi])).
+
 strip_slash(Url) ->
   case binary:last(Url) of
     $/ -> binary:part(Url, 0, byte_size(Url) - 1);

src/logic/logic_email_templates.erl

@@ -1,11 +1,28 @@
 -module(logic_email_templates).
--export([render/2]).
+-export([render/2, render_reminder/3]).
 
 %% Kind: verify | invite | reset
 -spec render(verify | invite | reset, binary()) ->
   {Subject :: binary(), Plain :: binary(), Html :: binary()}.
 render(Kind, Url) ->
   {Subject, Heading, Lead, Cta, Foot, Pre} = copy(Kind),
+  assemble(Subject, Heading, Lead, Url, Cta, Foot, Pre).
+
+%% Booking reminder (Back#70): title + when text in lead.
+-spec render_reminder(binary(), binary(), binary()) ->
+  {Subject :: binary(), Plain :: binary(), Html :: binary()}.
+render_reminder(Url, Title, WhenText) ->
+  Subject = <<"CalenTIQ: напоминание о записи">>,
+  Heading = <<"Напоминание о записи">>,
+  Lead = iolist_to_binary([
+    <<"Скоро: «">>, Title, <<"» — ">>, WhenText, <<" (UTC).">>
+  ]),
+  Cta = <<"Открыть запись">>,
+  Foot = <<"Вы получили письмо, потому что записаны на это событие в CalenTIQ.">>,
+  Pre = <<"Напоминание о записи в CalenTIQ">>,
+  assemble(Subject, Heading, Lead, Url, Cta, Foot, Pre).
+
+assemble(Subject, Heading, Lead, Url, Cta, Foot, Pre) ->
   Plain = iolist_to_binary([Heading, <<"\n\n">>, Lead, <<"\n\n">>, Url, <<"\n">>]),
   Html = fill(layout(), [
     {<<"{{preheader}}">>, Pre},

src/logic/logic_notification.erl

@@ -6,6 +6,7 @@
 -export([notify_event_update/1]).
 -export([notify_admin/2]).
 -export([notify_specialist_invite/2]).
+-export([notify_event_reminder/2]).
 
 %% Уведомление о бронировании
 notify_booking(UserId, Booking) ->
@@ -45,6 +46,13 @@ notify_specialist_invite(UserId, Invite) ->
   },
   broadcast_to_user(UserId, specialist_invite, Data).
 
+%% In-app / WS: напоминание о записи (Back#70)
+notify_event_reminder(UserId, #{title := Title, when_text := WhenText} = Data) ->
+  NTitle = <<"Напоминание о записи">>,
+  Body = iolist_to_binary([<<"Скоро: «">>, Title, <<"» — ">>, WhenText, <<" (UTC)">>]),
+  _ = core_notification:create(UserId, event_reminder, NTitle, Body),
+  broadcast_to_user(UserId, event_reminder, Data#{user_id => UserId}).
+
 %% Уведомление для администраторов
 notify_admin(Type, Data) ->
   Message = {admin_notification, Type, Data},