docs(claude): document SQLite store, refetch command, and phpstan script

Update the architecture diagram and env var table to reflect the
ContributionStore tier and incremental fetch, document the
graph:contributions:refetch command, and note composer phpstan next to
the existing test commands.

CLAUDE.md

@@ -99,6 +99,9 @@ vendor/bin/phpunit tests/Unit/Service/SvgRendererTest.php
 
 # Run tests matching a filter
 vendor/bin/phpunit --filter it_renders
+
+# Static analysis (PHPStan level 8)
+composer phpstan
 ```
 
 On Windows, run via WSL (If Docker Desctop is not):
@@ -190,20 +193,24 @@ There is no `composer.lock` in the repo. If you add or change dependencies, run
 
 ## Architecture
 
-Single-controller Symfony app with no database. The request flow:
+Single-controller Symfony app. Two-tier cache: a 1h filesystem SVG cache in front of a SQLite raw-data store, in front of the provider APIs. The request flow:
 
 ```
 GET /graph.svg?theme=dark|light
   └─ GraphController
        ├─ host check (ALLOWED_HOSTS env, optional)
        ├─ cache lookup (filesystem, 1h TTL, key = "graph_{theme}")
-       │    └─ on miss:
-       │         ├─ GitHubProvider  → GitHub GraphQL API (contributionCalendar query)
-       │         ├─ GitLabProvider  → GitLab REST /users/:id/events (paginated, 100/page)
-       │         └─ GiteaProvider   → Gitea REST /api/v1/users/:user/heatmap
-       │              each returns array<string, int>  (Y-m-d => count)
-       │              failures are caught and logged; remaining providers still render
-       │         └─ merge by date (sum counts across providers)
+       │    └─ on miss: ContributionAggregator::aggregate()
+       │         ├─ per configured provider: ContributionStore::latestDate($name)
+       │         │    → $since = latest - 3 days (trailing overlap), or null on first run
+       │         ├─ GitHubProvider  → GitHub GraphQL API (contributionCalendar query, bounded by $since/$until)
+       │         ├─ GitLabProvider  → GitLab REST /users/:id/events (paginated, 100/page, `after`/`before` bounded)
+       │         ├─ GiteaProvider   → Gitea REST /api/v1/users/:user/heatmap (filtered client-side by $since/$until)
+       │         │    each returns array<string, int>  (Y-m-d => count)
+       │         │    failures are caught and logged; remaining providers still render
+       │         ├─ ContributionStore::merge() persists fresh data per provider (SQLite upsert)
+       │         ├─ ContributionStore::all(sinceDays: 371) reads back the render window (source of truth)
+       │         ├─ ContributionStore::prune() drops rows older than CONTRIBUTIONS_RETENTION_DAYS
        │         └─ SvgRenderer::render()
        └─ Response: image/svg+xml, Cache-Control: public max-age=3600
 ```
@@ -212,7 +219,11 @@ GET /graph.svg?theme=dark|light
 
 **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 contributions → level 0, 1–3 → 1, 4–6 → 2, 7–9 → 3, 10+ → 4) mapped to GitHub's exact 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.
+**SVG 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.
+
+**ContributionStore:** PDO SQLite at `var/data/contributions.db` (also a Docker volume), table `contributions (provider, date unixtime, count)`. Keyed by `(provider, date)`, upserted via `INSERT ... ON CONFLICT`. Bounds every re-fetch to a 3-day trailing window off the last stored date per provider — the root fix for the full-365-day-refetch `MaxExecutionTimeError` that used to hit on every cache miss. `CONTRIBUTIONS_RETENTION_DAYS` controls how far back rows are kept (empty = forever).
+
+**`graph:contributions:refetch` command:** manual escape hatch (`src/Command/RefetchContributionsCommand.php`) that bypasses the incremental trailing-window fetch and re-pulls a full or explicit date range. Options: `--provider=github,gitlab` (comma-separated, default all configured), `--from=YYYY-MM-DD` (default 365 days ago), `--to=YYYY-MM-DD` (default today), `--all` (shorthand for `--from=2005-01-01`). Splits the requested range into ≤365-day chunks (GitHub's GraphQL window limit; also caps GitLab pagination per call) and merges each chunk into the store as it completes, so a large `--all` run can't reintroduce the original runaway-pagination timeout.
 
 ## Environment variables
 
@@ -224,5 +235,6 @@ GET /graph.svg?theme=dark|light
 | `GITLAB_URL`                               | No         | Defaults to `https://gitlab.com`             |
 | `GITEA_USER` / `GITEA_TOKEN` / `GITEA_URL` | For Gitea  | Token scope: `read:user`                     |
 | `ALLOWED_HOSTS`                            | No         | Comma-separated hostnames; empty = allow all |
+| `CONTRIBUTIONS_RETENTION_DAYS`             | No         | Days of history to keep in the SQLite store; empty = keep forever |
 
 Copy `.env` to `.env.local` for local development — `.env.local` is gitignored.