refactor: implement template-driven node tree and human-readable vault layout

Unified Node model: added template_id, fs_path, archived, sort_order fields.
Template registry: system templates embedded as JSON (folder/project/client/
document/recipe), with Registry for enabled/disabled/filtered access.
SafeDisplayNameToPathSegment: human-readable path segments with Cyrillic
support, illegal char replacement, uniqueness via numeric suffixes.
Sidebar refactored: system views (Today/Inbox/Activity) separate from
workspace tree. Creation menu built dynamically from enabled templates.
Create/Rename/Move: physical folder operations with fs_path update,
recursive descendant path updates.
DB migration 012: adds template_id, fs_path, archived columns.
Vault migration command: rebuilds fs_path for existing nodes.
Tests: safename, registry, node model, repository integration.
Docs: VAULT_LAYOUT.md, TEMPLATES.md, PLAN.md updated.
i18n: nav.system, nav.workspace, template.*, common.rename/archive,
migrate.* keys added to ru.json and en.json.

scripts/check-i18n.sh

@@ -23,6 +23,8 @@ ALLOWED_GO_CYRILLIC=(
   "internal/gui/index.html.go"
   "internal/i18n/catalog.go"
   "cmd/verstak-gui/main.go"
+  "internal/core/templates/safename.go"
+  "internal/core/templates/safename_test.go"
 )
 
 echo "=== Checking for hardcoded Cyrillic in source code ==="