feat(version): /api/version + build-time version/commit stamping

Add a VERSION file (0.1.0) and inject APP_VERSION/GIT_SHA/BUILD_DATE as Docker
build-args (both stages; Vite inlines them into the SPA). New public GET
/api/version returns app_version, git_sha, build_date and the Alembic head as the
database revision. deploy.sh and the localdev build pass the args.

Dockerfile

@@ -1,5 +1,15 @@
+# Build/version info, injected via --build-arg (defaults keep un-built/dev runs working).
+ARG APP_VERSION=dev
+ARG GIT_SHA=unknown
+ARG BUILD_DATE=
+
 # Stage 1: build the frontend SPA
 FROM node:20-alpine AS frontend
+ARG APP_VERSION
+ARG GIT_SHA
+ARG BUILD_DATE
+# Vite inlines VITE_*-prefixed env into the bundle at build time.
+ENV VITE_APP_VERSION=$APP_VERSION VITE_GIT_SHA=$GIT_SHA VITE_BUILD_DATE=$BUILD_DATE
 WORKDIR /fe
 COPY frontend/package.json ./
 RUN npm install
@@ -8,10 +18,16 @@ RUN npm run build
 
 # Stage 2: backend runtime, serving the built SPA
 FROM python:3.12-slim
+ARG APP_VERSION
+ARG GIT_SHA
+ARG BUILD_DATE
 ENV PYTHONDONTWRITEBYTECODE=1 \
     PYTHONUNBUFFERED=1 \
     PIP_NO_CACHE_DIR=1 \
-    PIP_DISABLE_PIP_VERSION_CHECK=1
+    PIP_DISABLE_PIP_VERSION_CHECK=1 \
+    APP_VERSION=$APP_VERSION \
+    GIT_SHA=$GIT_SHA \
+    BUILD_DATE=$BUILD_DATE
 
 WORKDIR /app