docs: update README with token configuration and Docker development instructions

README.md

@@ -104,11 +104,14 @@ All credentials are configured via environment variables — see [Deploy](#deplo
 
 ### GitHub
 
+**Fine-grained token (recommended):**
 1. Go to **Settings → Developer settings → Personal access tokens → Fine-grained tokens**
 2. Set **Resource owner** to your account
 3. Under **Permissions → Account permissions**, set **Contribution activity** → Read-only
 4. Generate and copy the token
 
+**Classic token:** create a token with the `read:user` scope.
+
 ### GitLab
 
 1. Go to **User Settings → Access Tokens**
@@ -125,6 +128,8 @@ All credentials are configured via environment variables — see [Deploy](#deplo
 
 ## Development
 
+### Local (PHP)
+
 ```bash
 # Install deps
 composer install
@@ -136,24 +141,76 @@ APP_ENV=dev php -S localhost:8080 -t public
 curl "http://localhost:8080/graph.svg" -o graph.svg
 ```
 
+### Docker (recommended)
+
+`docker-compose.override.yml` is picked up automatically and targets the `dev` stage (Xdebug enabled, source mounted).
+
+```bash
+# Start dev container
+docker compose up -d --build
+
+# Shell into the container
+docker compose exec graph sh
+
+# Run tests inside the container
+docker compose exec graph php bin/phpunit
+
+# Disable Xdebug for faster test runs
+XDEBUG_MODE=off docker compose up -d
+```
+
+Xdebug listens on port **9003**. On Linux, `host.docker.internal` is resolved via `host-gateway`.
+
+To run with production config only (no override):
+
+```bash
+docker compose -f docker-compose.yml up -d --build
+```
+
+---
+
+## Testing
+
+```bash
+# Run full suite
+php bin/phpunit
+
+# Human-readable output
+php bin/phpunit --testdox
+
+# Single file
+php bin/phpunit tests/Unit/Service/SvgRendererTest.php
+
+# Filter by name
+php bin/phpunit --filter it_renders
+```
+
 ---
 
 ## Architecture
 
 ```
-GET /graph.svg
+GET /graph.svg?theme=dark|light
-      │
+  └─ GraphController
-      ├─ GitHubProvider  →  GitHub GraphQL API (contributionCalendar)
+       ├─ host check (ALLOWED_HOSTS env, optional)
-      ├─ GitLabProvider  →  GitLab REST API    (/users/:id/events)
+       ├─ cache lookup (filesystem, 1h TTL, key = "graph_{theme}")
-      └─ GiteaProvider   →  Gitea REST API     (/users/:user/heatmap)
+       │    └─ on miss:
-                │
+       │         ├─ GitHubProvider  → GitHub GraphQL API (contributionCalendar)
-          merge by date (sum counts)
+       │         ├─ GitLabProvider  → GitLab REST API    (/users/:id/events, paginated)
-                │
+       │         └─ GiteaProvider   → Gitea REST API     (/users/:user/heatmap)
-          SvgRenderer
+       │              each returns array<string, int>  (Y-m-d => count)
-                │
+       │              failures are caught and logged; remaining providers still render
-          image/svg+xml  (cached 1h)
+       │         └─ merge by date (sum counts across providers)
+       │         └─ SvgRenderer::render()
+       └─ Response: image/svg+xml, Cache-Control: public max-age=3600
 ```
 
+**Provider activation:** a provider only runs when its env vars are non-empty. GitHub and GitLab require `_USER` + `_TOKEN`; Gitea additionally requires `_URL`. GitLab resolves a numeric user ID from the username via a `/api/v4/users?username=` lookup before fetching events.
+
+**SvgRenderer:** builds a 53-column × 7-row grid aligned so the last column always ends on the Saturday of the current week. Five intensity levels (0 → level 0, 1–3 → 1, 4–6 → 2, 7–9 → 3, 10+ → 4) mapped to GitHub's colour tokens. No external assets — the SVG is fully self-contained.
+
+**Cache:** filesystem adapter (`var/cache/`), mounted as a Docker volume to survive container restarts. Theme is part of the cache key so dark and light are cached independently.
+
 ---
 
 ## License