fix(discovery): add json tags to domain types

Without snake_case json tags, Go serializes fields as PascalCase (ID,
MarktName, etc.) — but the Svelte frontend reads snake_case. Every
row.id on the client was undefined, which made Svelte 5 see identical
'undefined' keys across the {#each queue as row (row.id)} loop and
throw each_key_duplicate.

Adds explicit snake_case tags to Bucket, DiscoveredMarket, and
RejectedDiscovery to match what the TypeScript types already expect.

backend/internal/domain/discovery/model.go

@@ -9,47 +9,47 @@ import (
 
 // Bucket is a scheduler row: one (land, region, year_month) tuple.
 type Bucket struct {
-	ID            uuid.UUID
-	Land          string
-	Region        string
-	YearMonth     string // 'YYYY-MM'
-	LastQueriedAt *time.Time
-	LastError     string
-	CreatedAt     time.Time
+	ID            uuid.UUID  `json:"id"`
+	Land          string     `json:"land"`
+	Region        string     `json:"region"`
+	YearMonth     string     `json:"year_month"` // 'YYYY-MM'
+	LastQueriedAt *time.Time `json:"last_queried_at"`
+	LastError     string     `json:"last_error"`
+	CreatedAt     time.Time  `json:"created_at"`
 }
 
 // DiscoveredMarket is a queue entry awaiting admin review.
 type DiscoveredMarket struct {
-	ID               uuid.UUID
-	BucketID         uuid.UUID
-	MarktName        string
-	Stadt            string
-	Bundesland       string
-	Land             string
-	StartDatum       *time.Time
-	EndDatum         *time.Time
-	Website          string
-	Quellen          []string
-	Extraktion       string
-	Hinweis          string
-	NameNormalized   string
-	MatchedSeriesID  *uuid.UUID
-	Status           string // 'pending' | 'accepted' | 'rejected'
-	DiscoveredAt     time.Time
-	ReviewedAt       *time.Time
-	ReviewedBy       *uuid.UUID
-	CreatedEditionID *uuid.UUID
+	ID               uuid.UUID  `json:"id"`
+	BucketID         uuid.UUID  `json:"bucket_id"`
+	MarktName        string     `json:"markt_name"`
+	Stadt            string     `json:"stadt"`
+	Bundesland       string     `json:"bundesland"`
+	Land             string     `json:"land"`
+	StartDatum       *time.Time `json:"start_datum"`
+	EndDatum         *time.Time `json:"end_datum"`
+	Website          string     `json:"website"`
+	Quellen          []string   `json:"quellen"`
+	Extraktion       string     `json:"extraktion"`
+	Hinweis          string     `json:"hinweis"`
+	NameNormalized   string     `json:"name_normalized"`
+	MatchedSeriesID  *uuid.UUID `json:"matched_series_id"`
+	Status           string     `json:"status"` // 'pending' | 'accepted' | 'rejected'
+	DiscoveredAt     time.Time  `json:"discovered_at"`
+	ReviewedAt       *time.Time `json:"reviewed_at"`
+	ReviewedBy       *uuid.UUID `json:"reviewed_by"`
+	CreatedEditionID *uuid.UUID `json:"created_edition_id"`
 }
 
 // RejectedDiscovery stores a sticky rejection scoped to (normalized_name, city, year).
 type RejectedDiscovery struct {
-	ID             uuid.UUID
-	NameNormalized string
-	Stadt          string
-	Year           int
-	RejectedAt     time.Time
-	RejectedBy     *uuid.UUID
-	Reason         string
+	ID             uuid.UUID  `json:"id"`
+	NameNormalized string     `json:"name_normalized"`
+	Stadt          string     `json:"stadt"`
+	Year           int        `json:"year"`
+	RejectedAt     time.Time  `json:"rejected_at"`
+	RejectedBy     *uuid.UUID `json:"rejected_by"`
+	Reason         string     `json:"reason"`
 }
 
 // Pass0Response is the parsed shape of the Mistral Pass 0 agent reply.