feat(scaffold): Next 16 + Payload 3 scaffold with Kaniko CI and Swarm deploy

Initial app scaffold wired end-to-end: Payload 3.82 CMS integrated with Next
16.2 App Router (standalone output), PostgreSQL 17 adapter, Lexical rich text,
Tailwind 3 with Material 3 token palette ported from the stitch technical-
editorial design, self-hosted Space Grotesk + Inter via next/font, and
lucide-react icons. Admin lives at /admin, REST/GraphQL at /api/*, and
/api/health returns build SHA/REV for deploy verification.

Seven collections (Users, Media, Categories, Projects, Posts, Gear,
ContactSubmissions) and six globals (Home, About, Contact, Resume,
Navigation, SEO) model the content outlined in docs/PRD.md.

Multi-stage Dockerfile builds a non-root standalone runner; Woodpecker
pipeline lints, typechecks, builds, audits, builds with Kaniko to
git.mosaicstack.dev, scans with Trivy, and links the package. Swarm
compose mirrors the mosaic-stack-website Traefik entrypoints=web pattern
with www->apex redirect and immutable WEB_IMAGE_TAG.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.dockerignore

@@ -0,0 +1,19 @@
+**/node_modules
+**/.next
+**/dist
+**/coverage
+.git
+.gitignore
+.env
+.env.*
+!.env.example
+*.log
+Dockerfile*
+docker-compose*.yml
+.woodpecker
+.mosaic
+docs
+README.md
+LICENSE
+design-samples
+images