Status LEDs, image model selection, backup restore, provider test, monthly versions

- Sidebar: three status LEDs (server, models, MCP) with an overview popover (/api/status)
- Images: preview stage, purpose-based model choice and reference images
  (Nano Banana Pro edit refines the chosen preview)
- Settings: restore a stored or uploaded backup (staged, applied on restart)
- Provider form: test connection; saving or reloading re-checks the status at once
- opencode Zen/Go: send x-opencode-session with a stable id per conversation
- Releases are named vYYYYMM-NNNNN; scripts/release.sh numbers, tags, builds and publishes
- Fix: backups made in the same second no longer overwrite each other

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

core/src/provider/anthropic.rs

@@ -168,7 +168,8 @@ impl Provider for Anthropic {
         for (k, v) in &req.model.options {
             body[k] = v.clone();
         }
-        let resp = self.request(reqwest::Method::POST, "/messages").json(&body).send().await?;
+        let rb = self.request(reqwest::Method::POST, "/messages").json(&body);
+        let resp = self.ep.with_session(rb, req.session_id.as_deref()).send().await?;
         if !resp.status().is_success() {
             return Err(http_error(resp).await);
         }