chore: align repository development defaults (#14)

Align editor defaults with this repository’s languages and existing
tools, preserve generated files and binary assets, and fill the missing
Git/configuration defaults.

Changed files: `.editorconfig`, `.gitattributes`.

Validation: EditorConfig resolution, Git attributes and ignore probes,
configuration parsing, whitespace checks, repository commit/push hooks
where provided, and redacted secret scans passed. The full diff received
a separate self-review. Application source is unchanged.

Author: bolens

.editorconfig

@@ -0,0 +1,29 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 2
+
+[*.{md,mdx}]
+trim_trailing_whitespace = false
+
+[*.py]
+indent_style = space
+indent_size = 4
+
+# Preserve captured configuration and recovery snapshots on save.
+[*.{cfg,conf,bkp}]
+trim_trailing_whitespace = false
+insert_final_newline = unset
+end_of_line = unset
+
+# Lockfiles are written by their owning tool.
+[devenv.lock]
+indent_style = unset
+indent_size = unset
+trim_trailing_whitespace = unset
+insert_final_newline = unset

.gitattributes

@@ -0,0 +1,2 @@
+# Normalize detected text while preserving binary contents.
+* text=auto eol=lf