Overhaul: real metrics, Git integration UI, open-source hygiene, root cleanup

Backend:
- GET /services/:id/metrics with real Docker container stats
- DELETE /git/providers/:id and GET repo branches endpoint

Frontend:
- Service detail shows real telemetry or honest empty states
- Live status distinguishes idle/polling/reconnecting
- Git providers section in Settings; repo+branch pickers in Add Service
- Real logo, compact Projects header, canvas fitView fix
- index.css deduplicated (1725 -> 1384 lines)
- Fixed smoke tests, lint errors, ToastProvider/context unification

Repo hygiene:
- Added LICENSE (MIT), CONTRIBUTING.md, SECURITY.md; rewrote README
- Untracked .env.prod and data/letsencrypt secrets; fixed .gitignore
- Removed legacy root src/internal/cmd and stale configs/docs/artifacts
- Moved guides and design references under docs/

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

CONTRIBUTING.md

@@ -0,0 +1,42 @@
+# Contributing to Containr
+
+Thanks for your interest in contributing. Containr is a self-hosted deployment
+platform — contributions of all sizes are welcome.
+
+## Project Layout
+
+```
+app/backend/    Go control-plane API (Gin, PostgreSQL, Redis, Docker SDK)
+app/frontend/   React + Vite + TypeScript dashboard
+infra/          Self-hosted compose stack (Traefik, Cloudflare Tunnel)
+docs/           Guides, API spec, and design documents
+templates/      Service template catalog notes
+```
+
+## Development Setup
+
+1. Copy `.env.example` to `.env` and fill in values (never commit `.env`).
+2. Start Postgres and Redis: `docker compose up -d postgres redis`
+3. Backend: `cd app/backend && go run ./cmd/server`
+4. Frontend: `cd app/frontend && npm install && npm run dev`
+
+## Checks Before Submitting
+
+- Backend: `cd app/backend && go build ./... && go test ./... && go vet ./...`
+- Frontend: `cd app/frontend && npm run build && npm test`
+- Compose: `docker compose config -q`
+
+## Conventions
+
+- Reuse existing utilities before adding dependencies.
+- Keep handlers thin; business logic lives in `internal/` packages.
+- Regenerate API types after schema changes:
+  `npm --prefix app/frontend run generate:api`.
+- Never commit secrets, tokens, or environment files.
+- Write tests for non-trivial logic.
+
+## Pull Requests
+
+- Keep PRs focused — one concern per PR.
+- Describe the "why", not just the "what".
+- Include a test plan for anything touching deployment, auth, or networking.