Add node peers, blue banners, glowing diff ranges, fix back navigation

- Show Bitcoin Core peer count on block height card (hover for in/out)
- BestSharePage disclaimers now use solid blue styling
- Difficulty distribution ranges glow from warm peach to deep red
- Back-to-dashboard buttons always navigate to dashboard instead of
  using browser history

api/internal/bitcoind/rpc.go

@@ -343,6 +343,20 @@ func (c *RPC) GetRawMempoolVerbose(ctx context.Context) (map[string]RawMempoolEn
 	return out, nil
 }
 
+type NetworkInfo struct {
+	Connections    int `json:"connections"`
+	ConnectionsIn  int `json:"connections_in"`
+	ConnectionsOut int `json:"connections_out"`
+}
+
+func (c *RPC) GetNetworkInfo(ctx context.Context) (*NetworkInfo, error) {
+	var out NetworkInfo
+	if err := c.Call(ctx, "getnetworkinfo", nil, &out); err != nil {
+		return nil, err
+	}
+	return &out, nil
+}
+
 // IsRPCError checks if err is an rpcError with a specific code.
 func IsRPCError(err error, code int) bool {
 	var rerr *rpcError