feat(dashboardapi): walking skeleton for graph-aware Grafana generator (#34)

Encrypts the Grafana bearer token via Node-RED credentials block instead of
plain config (F-11). Adds folderUid config field threaded through to the
buildUpsertRequest payload (F-8, resolves PRD O-5). Migration path: legacy
plain bearerToken still loads, with one-time warn() prompting user to re-save.

Composition + URL + headers + per-instance UID were already in place; only
the credentials + folderUid + tests are new.

- dashboardAPI.html: bearerToken moved to credentials block; folderUid added.
- dashboardAPI.js: registerType options pass credentials descriptor.
- src/nodeClass.js: read token from node.credentials; legacy fallback warns.
- src/specificClass.js: buildUpsertRequest emits folderUid when set.
- src/commands/handlers.js: pass folderUid from config to buildUpsertRequest.
- test/basic/slice34-credentials-and-folder.basic.test.js: 5 new tests.

Diff-based regeneration (F-1) and the explicit flows:started lifecycle hook
land in #36 once the S1 spike predicate is wired. Until then, the existing
child.register message trigger continues to drive composition on every
startup-time child registration.

Closes #34

src/nodeClass.js

@@ -30,6 +30,18 @@ class nodeClass {
 
   _buildConfig(uiConfig) {
     const cfgMgr = new configManager();
+    // Credentials block (Node-RED encrypts at rest in flow_cred.json). Legacy
+    // installs may still carry bearerToken on uiConfig — fall back with a
+    // one-time deprecation warning so the user knows to re-save.
+    const credentialToken = this.node?.credentials?.bearerToken || '';
+    const legacyToken = uiConfig.bearerToken || '';
+    if (!credentialToken && legacyToken) {
+      this.RED?.log?.warn?.(
+        `[${this.name}] bearer token loaded from legacy plain config field. ` +
+        `Re-open this node in the editor and click Done to migrate to encrypted credentials.`
+      );
+    }
+    const bearerToken = credentialToken || legacyToken;
     return cfgMgr.buildConfig(this.name, uiConfig, this.node.id, {
       functionality: {
         softwareType: this.name.toLowerCase(),
@@ -39,7 +51,8 @@ class nodeClass {
         protocol: uiConfig.protocol || 'http',
         host: uiConfig.host || 'localhost',
         port: Number(uiConfig.port || 3000),
-        bearerToken: uiConfig.bearerToken || '',
+        bearerToken,
+        folderUid: uiConfig.folderUid || '',
       },
       defaultBucket: uiConfig.defaultBucket || process.env.INFLUXDB_BUCKET || '',
     });