Add Gitea Action to build and push the image for Komodo deploys

Multi-stage Dockerfile builds the web bundle, embeds it into the static
Go binary (CGO_ENABLED=0), and ships it in a minimal alpine runtime:
non-root user, ca-certificates + tzdata, SQLite on a /data volume,
healthcheck on /api/v1/healthz, OCI provenance labels.

build-image.yml pushes to the Gitea registry on every branch push:
  * main             -> :latest
  * any other branch -> :<branch-name> (sanitized to valid tag chars)
  * every build      -> :sha-<short>   (immutable, for pinning)

A push to a PR branch covers the PR, so there is no separate
pull_request trigger. README documents the image, tags, and a
docker run / Komodo compose snippet. Modeled on mort's CI.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01JdQpdYYsTgtkJBxbcpAszi

.dockerignore

@@ -0,0 +1,26 @@
+# VCS / editor / docs — not needed in the image build context.
+.git
+.gitea
+.github
+.idea
+.vscode
+*.md
+LICENSE
+
+# Local build outputs and databases.
+/pansy
+*.db
+*.db-wal
+*.db-shm
+
+# Frontend deps/output are rebuilt inside the image's web stage.
+web/node_modules
+web/dist
+
+# The embedded web build is produced fresh in the image (web stage → embed
+# directory), so never ship stale local contents. dist.go itself is kept.
+internal/webdist/dist
+
+# Assorted local scratch.
+.playwright-mcp
+.claude