refactor(stockholm): extract kiloDefaultValue with provenance comment

The Stockholm "kilo" constant (a7928d7b43dcd49f0af31e5aeed26458) was
duplicated as a string literal in bridge.go and state.go. To a future
reader the hex blob can read like a leaked secret, which it is not —
it's a published default carried over from the upstream
krahl/soundcork-stockholm-app project (BackendApplication.java). The
Stockholm JS expects exactly this value via getConstant("kilo") when
nothing else has stored a different one.

Promote to a named const in util.go with the explanation, and reference
it from both call sites. Tests keep the literal so they continue to
catch any accidental change to the wire value.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

pkg/service/stockholm/bridge.go

@@ -140,7 +140,7 @@ func (b *Bridge) dispatch(clientID string, req appSendRequest) {
 		val := b.state.Get("constant." + name)
 
 		if val == "" && name == "kilo" {
-			val = "a7928d7b43dcd49f0af31e5aeed26458"
+			val = kiloDefaultValue
 		}
 
 		b.enqueueResult(clientID, id, val, "")

pkg/service/stockholm/state.go

@@ -65,9 +65,8 @@ func (s *NativeState) SeedFromEnv(cfg *Config) {
 		updates["margeAccountID"] = v
 	}
 
-	// Default constant
 	if s.Get("constant.kilo") == "" {
-		updates["constant.kilo"] = "a7928d7b43dcd49f0af31e5aeed26458"
+		updates["constant.kilo"] = kiloDefaultValue
 	}
 
 	// First-run defaults that require a persisted value

pkg/service/stockholm/util.go

@@ -5,6 +5,15 @@ import (
 	"encoding/hex"
 )
 
+// kiloDefaultValue is the published default for the Stockholm "kilo"
+// constant, carried over from the upstream krahl/soundcork-stockholm-app
+// project (BackendApplication.java). Not a secret — this is the exact
+// value the Stockholm JS expects to read via getConstant("kilo") when
+// nothing else has stored a different one. Seeded into NativeState on
+// first run; also returned by the bridge as a fallback if the state
+// entry is missing.
+const kiloDefaultValue = "a7928d7b43dcd49f0af31e5aeed26458"
+
 func randomHexUUID() string {
 	b := make([]byte, 16)
 	_, _ = rand.Read(b)