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>

android/keystore.properties.example

@@ -0,0 +1,11 @@
+# Copy to android/keystore.properties (gitignored) and fill in real values.
+# The release keystore itself must live OUTSIDE the repository or be gitignored.
+#
+# IMPORTANT: the previous keystore (android/app/appKeyStore) was committed to
+# git history — treat it as compromised. Generate a NEW keystore:
+#   keytool -genkeypair -v -storetype PKCS12 -keystore procurelinc-release.keystore \
+#     -alias procurelinc -keyalg RSA -keysize 2048 -validity 10000
+storeFile=../procurelinc-release.keystore
+storePassword=CHANGE_ME
+keyAlias=procurelinc
+keyPassword=CHANGE_ME