Add Docker deploy and Gitea Actions CI, plus a local testing guide

Dockerfile/docker-compose.yml mirror keep's pattern — same
better-sqlite3 native-addon build story, same pull_policy: always +
named volume for the SQLite DB so redeploys don't lose captured
articles. Gitea Actions workflow builds and pushes to the Gitea
container registry on push to main (needs a TKNTKN repo secret, same
as keep/wisp/npm-statuspage).

TESTING.md is the step-by-step for running the server + loading the
extension unpacked, written up from what was actually verified
end-to-end in the previous session.

Verified: image builds, server starts and responds inside the
container, capture works, and data survives a container restart.

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

Dockerfile

@@ -0,0 +1,25 @@
+FROM node:22-alpine AS build
+WORKDIR /app
+# better-sqlite3 has a native addon with no prebuilt binary for this
+# platform/Node combo yet — build it from source.
+RUN apk add --no-cache python3 make g++
+COPY package*.json ./
+RUN npm install
+COPY . .
+RUN npm run build
+
+FROM node:22-alpine
+WORKDIR /app
+# Same native-addon rebuild needed for the production-only install below;
+# the toolchain is purged again afterward to keep the runtime image lean.
+RUN apk add --no-cache python3 make g++
+COPY package*.json ./
+RUN npm install --omit=dev && apk del python3 make g++
+COPY --from=build /app/dist ./dist
+
+# DATA_DIR (SQLite DB) is a mutable runtime volume — not baked into the
+# image, so redeploys don't clobber captured articles.
+ENV DATA_DIR=/app/data
+
+EXPOSE 3070
+CMD ["node", "dist/server/index.js"]