graph/db: fix SetSourceNode race with lenient upsert

This commit fixes a race condition where multiple goroutines call
SetSourceNode concurrently during startup, causing sql.ErrNoRows
errors. The race occurs when multiple code paths (setSelfNode,
createNewHiddenService, RPC updates) read the same old timestamp,
independently increment it to the same new value (T+1), and race to
write.

The fix uses the new UpsertSourceNode SQL query (without strict
timestamp constraint) instead of UpsertNode. This allows
last-write-wins semantics for our own node, ensuring all parameter
changes persist even when timestamps collide.

Refactored sql_store.go for reusability:
- upsertNodeAncillaryData: common logic for features/addresses/extras
- populateNodeParams: common parameter building with callback pattern
- buildNodeUpsertParams: builds params for strict UpsertNode
- buildSourceNodeUpsertParams: builds params for lenient UpsertSourceNode
- upsertSourceNode: new function using lenient query

Updated TestSetSourceNodeSameTimestamp to verify that concurrent
updates with the same timestamp now succeed and parameter changes
persist.

Fixes the itest error:
"unable to upsert source node: upserting node(...): sql: no rows in
result set"

graph/db/graph_test.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"context"
 	"crypto/sha256"
-	"database/sql"
 	"encoding/hex"
 	"errors"
 	"fmt"
@@ -397,19 +396,19 @@ func TestSourceNode(t *testing.T) {
 	compareNodes(t, testNode, sourceNode)
 }
 
-// TestSetSourceNodeSameTimestamp demonstrates that SetSourceNode can return an
-// error when called with the same last update timestamp. Calling SetSourceNode
-// with the same timestamp should be allowed (unlike AddNode), as it is
-// possible that our own node announcement may change quickly. This will be
-// fixed in an upcoming commit.
+// TestSetSourceNodeSameTimestamp tests that SetSourceNode accepts updates
+// with the same timestamp. This is necessary because multiple code paths
+// (setSelfNode, createNewHiddenService, RPC updates) can race during startup,
+// reading the same old timestamp and independently incrementing it to the same
+// new value. For our own node, we want parameter changes to persist even with
+// timestamp collisions (unlike network gossip where same timestamp means same
+// content).
 func TestSetSourceNodeSameTimestamp(t *testing.T) {
 	t.Parallel()
 	ctx := t.Context()
 
 	graph := MakeTestGraph(t)
 
-	_, isSQLStore := graph.V1Store.(*SQLStore)
-
 	// Create and set the initial source node.
 	testNode := createTestVertex(t)
 	require.NoError(t, graph.SetSourceNode(ctx, testNode))
@@ -421,8 +420,9 @@ func TestSetSourceNodeSameTimestamp(t *testing.T) {
 
 	// Create a modified version of the node with the same timestamp but
 	// different parameters (e.g., different alias and color). This
-	// could well be the case for our own node announcement (unlike other
-	// announcements where same timestamp means same parameters).
+	// simulates the race condition where multiple goroutines read the
+	// same old timestamp, independently increment it, and try to update
+	// with different changes.
 	modifiedNode := models.NewV1Node(
 		testNode.PubKeyBytes, &models.NodeV1Fields{
 			// Same timestamp.
@@ -437,20 +437,20 @@ func TestSetSourceNodeSameTimestamp(t *testing.T) {
 	)
 
 	// Attempt to set the source node with the same timestamp but
-	// different parameters.
-	err = graph.SetSourceNode(ctx, modifiedNode)
+	// different parameters. This should now succeed for both SQL and KV
+	// stores. The SQL store uses UpsertSourceNode which removes the
+	// strict timestamp constraint, allowing last-write-wins semantics.
+	require.NoError(t, graph.SetSourceNode(ctx, modifiedNode))
 
-	// The SQL store will return sql.ErrNoRows because the UPDATE clause
-	// in the upsert query requires the new timestamp to be strictly
-	// greater than the existing one. When this condition is not met, no
-	// rows are updated and the SQL query returns ErrNoRows. The bbolt KV
-	// store, on the other hand, silently ignores stale updates and returns
-	// no error.
-	if isSQLStore {
-		require.ErrorIs(t, err, sql.ErrNoRows)
-	} else {
-		require.NoError(t, err)
-	}
+	// Verify that the parameter changes actually persisted.
+	updatedNode, err := graph.SourceNode(ctx)
+	require.NoError(t, err)
+	require.Equal(t, "different-alias", updatedNode.Alias.UnwrapOr(""))
+	require.Equal(
+		t, color.RGBA{R: 100, G: 200, B: 50, A: 0},
+		updatedNode.Color.UnwrapOr(color.RGBA{}),
+	)
+	require.Equal(t, testNode.LastUpdate, updatedNode.LastUpdate)
 }
 
 // TestEdgeInsertionDeletion tests the basic CRUD operations for channel edges.