feat(io): add AsterReader module for Code Aster .med/.rmed files

New 25-line AsterReader module:
- Module wrapper for Code Aster reader (requires HDF5.jl)
- Includes: read_aster_mesh.jl, read_aster_results.jl
- Exports: aster_read_mesh
- parse_node_id(): utility for parsing node IDs from names
- Requires HDF5.jl (optional dependency, conditionally loaded)

Provides Code Aster .med/.rmed file reading infrastructure.

src/io/AsterReader.jl

@@ -0,0 +1,25 @@
+# This file is a part of JuliaFEM.
+# License is MIT: see https://github.com/JuliaFEM/AsterReader.jl/blob/master/LICENSE
+
+module AsterReader
+
+using HDF5
+
+"""
+    parse_node_id(node_name)
+
+Return id number from node name. Usually the node name contains the id number,
+i.e. N123 => 123 and so on.
+
+"""
+function parse_node_id(node_name)
+    m = match(r"\d+", node_name)
+    m != nothing || error("Unable to parse id from node name $node_name.")
+    return tryparse(Int, m.match)
+end
+
+include("read_aster_mesh.jl")
+include("read_aster_results.jl")
+export aster_read_mesh
+
+end