graph/db: add versioned HasChannelEdge method

Add a new HasChannelEdge method that takes a gossip version parameter
and returns only existence and zombie status, without timestamp data.
This supports both v1 and v2 gossip protocols.

The original HasChannelEdge method is renamed to HasV1ChannelEdge to
preserve v1-specific functionality for callers that need timestamp
information. All call sites are updated accordingly.

The SQL store implementation now handles both gossip versions, using
timestamps for v1 and block heights for v2 policies, with proper
reject cache support for both versions.

graph/db/reject_cache.go

@@ -59,7 +59,6 @@ type rejectCacheEntry struct {
 	flags rejectFlags
 }
 
-// newRejectCacheEntryV1 constructs a reject cache entry for v1 policies.
 func newRejectCacheEntryV1(upd1, upd2 time.Time, exists,
 	isZombie bool) rejectCacheEntry {
 
@@ -70,7 +69,6 @@ func newRejectCacheEntryV1(upd1, upd2 time.Time, exists,
 	}
 }
 
-// newRejectCacheEntryV2 constructs a reject cache entry for v2 policies.
 func newRejectCacheEntryV2(upd1, upd2 uint32, exists,
 	isZombie bool) rejectCacheEntry {
 
@@ -81,7 +79,6 @@ func newRejectCacheEntryV2(upd1, upd2 uint32, exists,
 	}
 }
 
-// updateRejectCacheEntryV1 updates the cached v1 timestamps.
 func updateRejectCacheEntryV1(entry *rejectCacheEntry, isUpdate1 bool,
 	lastUpdate time.Time) {
 
@@ -92,7 +89,6 @@ func updateRejectCacheEntryV1(entry *rejectCacheEntry, isUpdate1 bool,
 	}
 }
 
-// updateRejectCacheEntryV2 updates the cached v2 block heights.
 func updateRejectCacheEntryV2(entry *rejectCacheEntry, isUpdate1 bool,
 	blockHeight uint32) {
 
@@ -104,8 +100,7 @@ func updateRejectCacheEntryV2(entry *rejectCacheEntry, isUpdate1 bool,
 }
 
 // rejectCacheKey uniquely identifies a channel entry in the reject cache by
-// gossip version and channel ID. This allows v1 and v2 policy state for the
-// same channel ID to be cached independently.
+// gossip version and channel ID.
 type rejectCacheKey struct {
 	version lnwire.GossipVersion
 	chanID  uint64