docs: add docs-as-code process and one ADR per feature

docs/docs-as-code.md defines the workflow; docs/adr holds 31 ADRs
(retroactive, reconstructed from code and changelog) with a template and
index. docs/check-docs.sh validates ADR structure, index, cited code
paths, relative links and CLAUDE.md/AGENTS.md sync.

docs/adr/0022-localization-seven-languages.md

@@ -0,0 +1,23 @@
+# 0022. In-code localization table for seven languages
+
+- **Status:** Accepted
+- **Area:** UI
+- **Recorded:** 2026-11-03 (retroactive: reconstructed from code, comments and changelog)
+
+## Context
+
+The wallet targets users across several markets and must work offline, with the strings available identically on every platform.
+
+## Decision
+
+`Loc` holds a key → 7-language table (it, en, es, fr, pt, de, zh). XAML uses `{Binding Loc[key]}`, C# uses `Loc.Tr("key")`. On language change the `Loc` instance is replaced so bindings refresh. An unknown language falls back to English. The picker in the Settings overlay is a hand-written list of `RadioButton`s bound to `IsLangXx` properties, so a new language needs a column, a button and a property.
+
+## Consequences
+
+- No resource-file tooling and no runtime lookup failures.
+- Adding a language touches three places; forgetting the picker leaves it unreachable.
+
+## References
+
+- `src/App/Localization/Loc.cs`
+- `src/App/ViewModels/MainWindowViewModel.Settings.cs`