fix: nil slice -> empty slice in list API responses

Backend:
- ListStorageJobs, ListSambaShares, ListNFSExports, ListUsers,
  ListDirty, ListApplyLog, ListWatchedMounts: initialize with
  make([]T, 0) instead of var x []T to avoid JSON null on empty.
  Fixes "Cannot read properties of null" crash on /storage.

Frontend:
- Storage.tsx: defensive setJobs(res.jobs ?? []) to guard against
  API returning null.

Tests:
- Add TestListStorageJobsEmptyReturnsSlice.

Version: 0.7.1

internal/db/queries.go

@@ -114,7 +114,7 @@ func (d *DB) ListDirty() ([]DirtyModule, error) {
 	}
 	defer rows.Close()
 
-	var modules []DirtyModule
+	modules := make([]DirtyModule, 0)
 	for rows.Next() {
 		var module DirtyModule
 		var markedAt string
@@ -158,7 +158,7 @@ func (d *DB) ListApplyLog(limit int) ([]ApplyLogEntry, error) {
 	}
 	defer rows.Close()
 
-	var entries []ApplyLogEntry
+	entries := make([]ApplyLogEntry, 0)
 	for rows.Next() {
 		var entry ApplyLogEntry
 		var success int
@@ -182,7 +182,7 @@ func (d *DB) ListSambaShares() ([]SambaShare, error) {
 	}
 	defer rows.Close()
 
-	var shares []SambaShare
+	shares := make([]SambaShare, 0)
 	for rows.Next() {
 		share, err := scanSambaShare(rows)
 		if err != nil {

internal/db/queries_nfs.go

@@ -77,7 +77,7 @@ func (d *DB) ListNFSExports() ([]NFSExport, error) {
 	}
 	defer rows.Close()
 
-	var exports []NFSExport
+	exports := make([]NFSExport, 0)
 	for rows.Next() {
 		export, err := scanNFSExport(rows)
 		if err != nil {

internal/db/queries_storage.go

@@ -170,7 +170,7 @@ func (d *DB) ListStorageJobs(limit int) ([]StorageJob, error) {
 	}
 	defer rows.Close()
 
-	var jobs []StorageJob
+	jobs := make([]StorageJob, 0)
 	for rows.Next() {
 		j, err := scanStorageJob(rows)
 		if err != nil {

internal/db/queries_storage_test.go

@@ -0,0 +1,27 @@
+package db
+
+import (
+	"testing"
+)
+
+func TestListStorageJobsEmptyReturnsSlice(t *testing.T) {
+	d, err := Open(":memory:")
+	if err != nil {
+		t.Fatalf("open db: %v", err)
+	}
+	defer d.Close()
+	if err := d.Migrate(); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+
+	jobs, err := d.ListStorageJobs(50)
+	if err != nil {
+		t.Fatalf("ListStorageJobs: %v", err)
+	}
+	if jobs == nil {
+		t.Error("ListStorageJobs returned nil, want empty slice")
+	}
+	if len(jobs) != 0 {
+		t.Errorf("len(jobs) = %d, want 0", len(jobs))
+	}
+}

internal/db/queries_users.go

@@ -53,7 +53,7 @@ func (d *DB) ListUsers() ([]User, error) {
 	}
 	defer rows.Close()
 
-	var users []User
+	users := make([]User, 0)
 	for rows.Next() {
 		user, err := scanUser(rows)
 		if err != nil {

internal/db/queries_watched.go

@@ -24,7 +24,7 @@ func (d *DB) ListWatchedMounts() ([]WatchedMount, error) {
 	}
 	defer rows.Close()
 
-	var mounts []WatchedMount
+	mounts := make([]WatchedMount, 0)
 	for rows.Next() {
 		m, err := scanWatchedMount(rows)
 		if err != nil {