feat: architecture refactor — core layer, spreadsheet engine, envelope bidding, tests

- Add src/core/ (config, errors, events, http, observability, storage, query)
- Add src/Spreadsheet/ engine with native POI backend and Excel bridge
- Add Envelope C spreadsheet flow and tender bidding envelope modules
- Consolidate components into src/components/, remove legacy Component/ and Hooks/
- Add registration state/validation, auth session guard, profile edit modules
- Add unit tests across axios, redux, bidding, registration, encryption, core
- Add CI workflow, docs (architecture, audit, DSC API spec), keystore example
- Remove tracked keystore binary; ignore scripts.zip

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -0,0 +1,31 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  quality:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Unit tests
+        run: npx jest --ci
+
+      - name: Typecheck
+        run: npx tsc --noEmit
+
+      # Errors are blocking; style warnings are still being burned down.
+      # Tighten to --max-warnings=0 once `npx eslint .` exits 0 on main.
+      - name: Lint
+        run: npx eslint . --quiet