chore: reorganize repository structure

- Move docker-compose files to .docker/compose/
- Move docker-entrypoint.sh to .docker/
- Move DOCKER.md to .docker/README.md
- Move 16 implementation docs to docs/implementation/
- Delete test artifacts (block_test.txt, caddy_*.json)
- Update all references in Dockerfile, Makefile, tasks, scripts
- Add .github/instructions/structure.instructions.md for enforcement
- Update CHANGELOG.md

Root level reduced from 81 items to ~35 visible items.

.docker/compose/README.md

@@ -0,0 +1,50 @@
+# Docker Compose Files
+
+This directory contains all Docker Compose configuration variants for Charon.
+
+## File Descriptions
+
+| File | Purpose |
+|------|---------|
+| `docker-compose.yml` | Main production compose configuration. Base services and production settings. |
+| `docker-compose.dev.yml` | Development overrides. Enables hot-reload, debug logging, and development tools. |
+| `docker-compose.local.yml` | Local development configuration. Standalone setup for local testing. |
+| `docker-compose.remote.yml` | Remote deployment configuration. Settings for deploying to remote servers. |
+| `docker-compose.override.yml` | Personal local overrides. **Gitignored** - use for machine-specific settings. |
+
+## Usage Patterns
+
+### Production Deployment
+
+```bash
+docker compose -f .docker/compose/docker-compose.yml up -d
+```
+
+### Development Mode
+
+```bash
+docker compose -f .docker/compose/docker-compose.yml \
+               -f .docker/compose/docker-compose.dev.yml up -d
+```
+
+### Local Testing
+
+```bash
+docker compose -f .docker/compose/docker-compose.local.yml up -d
+```
+
+### With Personal Overrides
+
+Create your own `docker-compose.override.yml` in this directory for personal
+configurations (port mappings, volume paths, etc.). This file is gitignored.
+
+```bash
+docker compose -f .docker/compose/docker-compose.yml \
+               -f .docker/compose/docker-compose.override.yml up -d
+```
+
+## Notes
+
+- Always use the `-f` flag to specify compose file paths from the project root
+- The override file is automatically ignored by git - do not commit personal settings
+- See project tasks in VS Code for convenient pre-configured commands