feat(store): fetch contributions incrementally and persist history in SQLite

Bound each provider's startFetch()/resolveFetch() to an optional
since/until window, wire a SQLite-backed ContributionStore into
ContributionAggregator (fetch only the trailing window past the last
stored date, merge into the store, prune by CONTRIBUTIONS_RETENTION_DAYS),
and add a graph:contributions:refetch command to force a full or ranged
re-fetch in <=365-day chunks. This is the root fix for the full
365-day-refetch timeout that used to hit on every cache miss.

docker-compose.yml

@@ -20,9 +20,11 @@ services:
       GITEA_USER: "${GITEA_USER:-}"
       GITEA_TOKEN: "${GITEA_TOKEN:-}"
       GITEA_URL: "${GITEA_URL:-}"
+      CONTRIBUTIONS_RETENTION_DAYS: "${CONTRIBUTIONS_RETENTION_DAYS:-0}"
     volumes:
       - cache:/app/var/cache/prod/pools
       - logs:/app/var/log
+      - data:/app/var/data
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost:8080/health"]
       interval: 30s
@@ -33,3 +35,4 @@ services:
 volumes:
   cache:
   logs:
+  data: