Make new_suggestions and Send to Google Chat recoverable

MQ-167-01: a scheduled or manual batch now emits new_suggestions:{batchId}
in the transaction that first stores its Side quests, so the cards and
their notification commit together. A later round that fails, or a
failure recording the batch's end, no longer loses the event; a later
round's emit is a no-op by key; a notification that cannot be stored
fails that store, leaving no unannounced cards. Replenish batches still
never notify. finishBatch goes back to recording status only.

MQ-167-02: migration 0017 adds shopping_lists.chat_send_unconfirmed_at.
SendToChat records the send as begun before posting, clears it with
sent_to_chat_at once Google Chat accepts, and clears it alone when Chat
refuses. A post Chat does not answer, or one it accepts that cannot be
recorded, is ErrSendUnconfirmed (502 chat_unconfirmed, not retryable)
and leaves the marker, as does a crash mid-send; a repeat without resend
never reposts, and resend posts again. The Supply run screen re-reads
the list after a failed send, shows an unconfirmed send, offers no Retry
for it, and sends again only with resend.

Task: f0cd9d50-9c11-41be-a945-7bae9f5f28a4

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/shopping/chat.go

@@ -3,6 +3,7 @@ package shopping
 import (
 	"context"
 	"database/sql"
+	"errors"
 	"fmt"
 
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/chat"
@@ -16,10 +17,17 @@ import (
 // Chat (chat.PostSupplyRun): each dinner with its items still needed, and a
 // link to the Supply run. It records sent_to_chat_at and returns the list.
 //
-// A week is sent once: a Supply run already sent is returned as it is,
-// without posting again, unless resend is true. A week with no Supply run
-// is ErrListNotFound and one frozen into the Supply archive ErrFrozen. A
-// post that fails returns chat.PostSupplyRun's error and records nothing.
+// A week is sent once: a Supply run already sent, or with a send
+// unconfirmed, is returned as it is, without posting again, unless resend
+// is true. A week with no Supply run is ErrListNotFound and one frozen into
+// the Supply archive ErrFrozen.
+//
+// The send is recorded as begun, in chat_send_unconfirmed_at, before it is
+// posted, so a post whose outcome is lost is never taken for one never
+// made. A post Google Chat refuses, or that is never made, returns
+// chat.PostSupplyRun's error and clears it. A post Google Chat does not
+// answer, or one it accepts that cannot then be recorded, is
+// ErrSendUnconfirmed and leaves it, as does the process stopping mid-send.
 func (s *Service) SendToChat(ctx context.Context, weekStart store.LocalDate, resend bool) (List, error) {
 	s.sending.Lock()
 	defer s.sending.Unlock()
@@ -30,7 +38,7 @@ func (s *Service) SendToChat(ctx context.Context, weekStart store.LocalDate, res
 	if l.Status != StatusCurrent {
 		return List{}, ErrFrozen
 	}
-	if l.SentToChatAt != nil && !resend {
+	if (l.SentToChatAt != nil || l.ChatSendUnconfirmedAt != nil) && !resend {
 		return l, nil
 	}
 	name, err := household.WeekLabel(weekStart)
@@ -54,20 +62,42 @@ func (s *Service) SendToChat(ctx context.Context, weekStart store.LocalDate, res
 			groups[i].Items = append(groups[i].Items, item)
 		}
 	}
-	if err := s.chat.PostSupplyRun(ctx, weekStart, name, groups); err != nil {
-		return List{}, err
+	q := db.New(s.st.Writer)
+	n, err := q.BeginShoppingListChatSend(ctx, db.BeginShoppingListChatSendParams{
+		ChatSendUnconfirmedAt: sql.NullString{String: store.Now().String(), Valid: true},
+		UpdatedAt:             store.Now().String(),
+		ID:                    l.ID,
+	})
+	if err != nil {
+		return List{}, fmt.Errorf("shopping: record send to Google Chat begun: %w", err)
 	}
-	// The post is made: record it even if the client has gone.
+	if n != 1 {
+		return List{}, ErrFrozen
+	}
+	postErr := s.chat.PostSupplyRun(ctx, weekStart, name, groups)
+	// The post's outcome is known: record it even if the client has gone.
 	write, cancel := jobs.FinalWriteContext(ctx)
 	defer cancel()
+	if errors.Is(postErr, chat.ErrUnreachable) {
+		return List{}, fmt.Errorf("%w: %w", ErrSendUnconfirmed, postErr)
+	}
+	if postErr != nil {
+		if _, err := q.ClearShoppingListChatSend(write, db.ClearShoppingListChatSendParams{
+			UpdatedAt: store.Now().String(),
+			ID:        l.ID,
+		}); err != nil {
+			return List{}, errors.Join(postErr, fmt.Errorf("shopping: clear refused send to Google Chat: %w", err))
+		}
+		return List{}, postErr
+	}
 	now := store.Now().String()
-	n, err := db.New(s.st.Writer).MarkShoppingListSentToChat(write, db.MarkShoppingListSentToChatParams{
+	n, err = q.MarkShoppingListSentToChat(write, db.MarkShoppingListSentToChatParams{
 		SentToChatAt: sql.NullString{String: now, Valid: true},
 		UpdatedAt:    now,
 		ID:           l.ID,
 	})
 	if err != nil {
-		return List{}, fmt.Errorf("shopping: record sent to Google Chat: %w", err)
+		return List{}, fmt.Errorf("%w: record sent to Google Chat: %w", ErrSendUnconfirmed, err)
 	}
 	if n != 1 {
 		return List{}, ErrFrozen