ci(docker): versioned image builds + Gitea build/push workflow

Add comprehensive Docker image versioning and a Gitea Actions workflow
that builds and pushes both the API and web images to the
git.mancinas.io registry.

Versioning: both Dockerfiles take APP_VERSION / GIT_SHA / BUILD_DATE
build-args, surfaced as runtime ENV + OCI labels, so a running container
self-reports the exact commit it was built from. metadata-action emits a
tag set per build: semver (from vX.Y.Z git tags), branch ref,
sha-<short>, and latest (default branch only).

Also fix the Dockerfiles for the pnpm workspace: the old npm install
could not resolve the "@jorgecuadros/database": "workspace:*" protocol
dep and would abort the API build. Now pin pnpm 9.15.9 via corepack,
install --frozen-lockfile with node-linker=hoisted (flat tree so the
runtime stage copies a single node_modules), and build via --filter. The
API build stage gets python3/make/g++ for argon2's musl source compile.
Add .dockerignore to keep the build context lean and deterministic.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -1,5 +1,6 @@
 {
   "name": "jorgecuadros-platform",
+  "version": "0.1.0",
   "private": true,
   "workspaces": [
     "apps/*",