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/

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

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Tomas Dvorak
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.