fix: hapus invalid observability fields, pin wrangler v4

wrangler.toml

@@ -9,20 +9,10 @@ workers_dev = true
 
 # ── Observability ────────────────────────────────────────────────────────────
 [observability]
-enabled = false
-head_sampling_rate = 1
-
-[observability.logs]
 enabled = true
 head_sampling_rate = 1
-persist = true
 invocation_logs = true
 
-[observability.traces]
-enabled = true
-persist = true
-head_sampling_rate = 1
-
 # ── Environment Variables ───────────────────────────────────────────────────
 # [vars]
 # RELAY_TIMEOUT_MS = "30000"