test: add Vitest and Phase 1 pure-helper suite

Introduce automated testing to a project that had no test runner, no
test script and no CI. Vitest fits the existing Vite setup with near-zero
config; a standalone vitest.config.ts wires the @/ alias via
vite-tsconfig-paths and runs in the node environment, avoiding the app's
Tailwind/React/WASM plugins that pure-logic tests do not need.

Cover the cheapest, highest-value surface first: pure helpers with no DOM,
WASM or database. getNextSequence and cloneField (field.ts), the
charset/collation and SQLite integer-column reordering plus enum naming
(render-uttils.ts), and orderTables including the CircularDependencyError
cycle path that backs the Foreign Key Cycle Detection feature.

The build's tsc step is unaffected (plain tsc no-ops on the root config)
and the new files typecheck clean under strict and lint clean.

tsconfig.node.json

@@ -8,5 +8,5 @@
 
     "strict": true
   },
-  "include": ["vite.config.ts"]
+  "include": ["vite.config.ts", "vitest.config.ts"]
 }