Backend Phase C: Sync-Kern + Caddy behind-proxy

Sync-Kern:
- internal/sync/hlc.go: Hybrid Logical Clock (wall_ms<<16|counter)
  Tick/Now/After, global mutex, strikt monoton + kausal korrekt
- internal/sync/hlc_test.go: Unit-Tests (monoton, kausal, keine Duplikate)

Store-Schicht:
- internal/store/opstore.go: AppendOps idempotent via UNIQUE(client_id,
  client_seq) ON CONFLICT DO NOTHING; LWW-Projektion (list_create/
  rename/delete, item_add/update/remove) in derselben Transaktion;
  PullOps mit Cursor (seq > since, 500er Pages)
- internal/store/liststore.go: CreateList / GetLists / GetList
- internal/store/itemstore.go: GetItems (nicht-gelöschte Items)
- internal/store/suggeststore.go: Search (pg_trgm + LIKE-fallback, 10)

HTTP-Handler:
- internal/httpapi/lists.go: GET/POST /api/lists, GET /api/lists/{id}
- internal/httpapi/ops.go: POST /api/lists/{id}/ops (Push),
  GET /api/lists/{id}/ops (Pull ?since=)
- internal/httpapi/suggest.go: GET /api/suggestions?q=
- internal/httpapi/api.go: alle Routen verdrahtet (RequireAuth)

Deployment:
- deploy/Caddyfile.behind-proxy: auto_https off, trusted_proxies
- deploy/Caddyfile: X-Forwarded-Proto hinzugefügt, Kommentar aktualisiert
- deploy/docker-compose.yml: CADDY_HTTP_PORT + CADDY_HTTPS_PORT
- deploy/.env.example: Caddy-Port-Variablen dokumentiert

go build ./... && go vet ./... && go test ./... ✅
HLC-Tests: monoton, kausal, keine Duplikate ✅
AGENTS.md: Phase C vollständig ✅

backend/internal/store/liststore.go

@@ -0,0 +1,88 @@
+package store
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// List is the projection of a list row.
+type List struct {
+	ID        uuid.UUID  `json:"id"`
+	Name      string     `json:"name"`
+	OwnerID   uuid.UUID  `json:"owner_id"`
+	CreatedAt time.Time  `json:"created_at"`
+	UpdatedAt time.Time  `json:"updated_at"`
+	DeletedAt *time.Time `json:"deleted_at,omitempty"`
+	HLCTS     int64      `json:"hlc_ts"`
+}
+
+// ListStore provides read/write access to the lists projection.
+type ListStore struct {
+	pool *pgxpool.Pool
+}
+
+// NewListStore creates a ListStore backed by the given pool.
+func NewListStore(pool *pgxpool.Pool) *ListStore { return &ListStore{pool: pool} }
+
+// CreateList inserts a new list owned by ownerID.
+// In the MVP, list creation is a direct INSERT (no op required).
+// The caller is responsible for emitting a list_create op if desired for full
+// op-log coverage; for Phase C the REST endpoint does a direct insert.
+func (s *ListStore) CreateList(ctx context.Context, ownerID uuid.UUID, name string) (*List, error) {
+	var l List
+	err := s.pool.QueryRow(ctx, `
+		INSERT INTO lists (name, owner_id)
+		VALUES ($1, $2)
+		RETURNING id, name, owner_id, created_at, updated_at, hlc_ts`,
+		name, ownerID,
+	).Scan(&l.ID, &l.Name, &l.OwnerID, &l.CreatedAt, &l.UpdatedAt, &l.HLCTS)
+	if err != nil {
+		return nil, fmt.Errorf("liststore: create list: %w", err)
+	}
+	return &l, nil
+}
+
+// GetLists returns all non-deleted lists owned by ownerID, newest first.
+func (s *ListStore) GetLists(ctx context.Context, ownerID uuid.UUID) ([]List, error) {
+	rows, err := s.pool.Query(ctx, `
+		SELECT id, name, owner_id, created_at, updated_at, hlc_ts
+		FROM lists
+		WHERE owner_id = $1 AND deleted_at IS NULL
+		ORDER BY created_at DESC`,
+		ownerID,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("liststore: get lists: %w", err)
+	}
+	defer rows.Close()
+
+	var lists []List
+	for rows.Next() {
+		var l List
+		if err := rows.Scan(&l.ID, &l.Name, &l.OwnerID, &l.CreatedAt, &l.UpdatedAt, &l.HLCTS); err != nil {
+			return nil, fmt.Errorf("liststore: scan list row: %w", err)
+		}
+		lists = append(lists, l)
+	}
+	return lists, rows.Err()
+}
+
+// GetList returns a single non-deleted list, checking that userID is the owner.
+// Returns pgx.ErrNoRows if not found or not owned by userID.
+func (s *ListStore) GetList(ctx context.Context, listID, userID uuid.UUID) (*List, error) {
+	var l List
+	err := s.pool.QueryRow(ctx, `
+		SELECT id, name, owner_id, created_at, updated_at, hlc_ts
+		FROM lists
+		WHERE id = $1 AND owner_id = $2 AND deleted_at IS NULL`,
+		listID, userID,
+	).Scan(&l.ID, &l.Name, &l.OwnerID, &l.CreatedAt, &l.UpdatedAt, &l.HLCTS)
+	if err != nil {
+		return nil, fmt.Errorf("liststore: get list: %w", err)
+	}
+	return &l, nil
+}