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.

internal/core/storage/migrations_012.sql.go

@@ -0,0 +1,8 @@
+package storage
+
+// migration012 — add template_id, fs_path, archived columns to nodes.
+const migration012 = `
+ALTER TABLE nodes ADD COLUMN template_id TEXT NOT NULL DEFAULT '';
+ALTER TABLE nodes ADD COLUMN fs_path TEXT NOT NULL DEFAULT '';
+ALTER TABLE nodes ADD COLUMN archived INTEGER NOT NULL DEFAULT 0;
+`

internal/core/storage/storage.go

@@ -68,6 +68,7 @@ var migrationFiles = map[int]string{
 	9:  migration009,
 	10: migration010,
 	11: migration011,
+	12: migration012,
 }
 
 func (db *DB) runInitialSchema() error {