feat: persist participant-scoped proposal recovery

server/api/service.go

@@ -42,6 +42,9 @@ type SteamLoginProvider interface {
 type SessionIssuer interface {
 	Issue(context.Context, string, time.Duration, time.Time) (domain.Session, string, error)
 }
+type ProposalBackend interface {
+	Get(context.Context, string, string, time.Time) (domain.Proposal, error)
+}
 
 type AssignmentView struct {
 	MatchID           string    `json:"match_id"`
@@ -57,24 +60,25 @@ type AssignmentView struct {
 type AssignmentProvider func(context.Context, string, string, time.Time) (AssignmentView, error)
 
 type Service struct {
-	Sessions       *domain.SessionStore
-	SessionBackend SessionBackend
-	SessionIssuer  SessionIssuer
-	SteamLogin     SteamLoginProvider
-	Queue          *domain.Queue
-	Candidate      CandidateProvider
-	CandidateV2    CandidateProviderV2
-	QueueBackend   QueueBackend
-	Probe          ProbeProvider
-	Assignment     AssignmentProvider
-	Now            func() time.Time
-	Proposals      map[string]*domain.Proposal
-	RankedProfiles map[string]domain.RankedProfile
-	TierPolicy     domain.TierPolicy
-	RateLimiter    *RateLimiter
-	proposalMu     sync.Mutex
-	eventsMu       sync.Mutex
-	events         *eventHub
+	Sessions        *domain.SessionStore
+	SessionBackend  SessionBackend
+	SessionIssuer   SessionIssuer
+	SteamLogin      SteamLoginProvider
+	Queue           *domain.Queue
+	Candidate       CandidateProvider
+	CandidateV2     CandidateProviderV2
+	QueueBackend    QueueBackend
+	Probe           ProbeProvider
+	Assignment      AssignmentProvider
+	Now             func() time.Time
+	Proposals       map[string]*domain.Proposal
+	ProposalBackend ProposalBackend
+	RankedProfiles  map[string]domain.RankedProfile
+	TierPolicy      domain.TierPolicy
+	RateLimiter     *RateLimiter
+	proposalMu      sync.Mutex
+	eventsMu        sync.Mutex
+	events          *eventHub
 }
 
 func (s *Service) Handler() http.Handler {
@@ -413,6 +417,15 @@ func (s *Service) proposalMutation(w http.ResponseWriter, r *http.Request) {
 		s.proposalMu.Lock()
 		defer s.proposalMu.Unlock()
 		proposal, exists := s.Proposals[parts[0]]
+		if s.ProposalBackend != nil {
+			proposalValue, providerErr := s.ProposalBackend.Get(r.Context(), playerID, parts[0], s.now())
+			if providerErr != nil {
+				writeError(w, http.StatusNotFound, "not_found")
+				return
+			}
+			proposal = &proposalValue
+			exists = true
+		}
 		if !exists || proposal == nil || !proposal.HasParticipant(playerID) {
 			writeError(w, http.StatusNotFound, "not_found")
 			return