replace imap gmail sync with mbsync + maildir import, app password UI

- rewrite gmail-sync handler: mbsync downloads to local Maildir, then import to sqlite
- add app password field to google integration config and API
- gmail sync section independent from oauth in settings UI
- live mbsync progress streaming to job status
- recoverable failure email with instructions for overquota/auth errors
- sync meta persisted to job on failure for richer notifications

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/servers/queue/engine.ts

@@ -81,11 +81,16 @@ function kickLane(lane: string) {
   processNextInLane(lane);
 }
 
+function scheduleRetry(lane: string, delayMs: number) {
+  setTimeout(() => kickLane(lane), delayMs);
+}
+
 async function processNextInLane(lane: string) {
   try {
     const jobs = await listAllJobs();
+    const now = Date.now();
     const next = jobs
-      .filter((j) => j.lane === lane && j.status === 'queued')
+      .filter((j) => j.lane === lane && j.status === 'queued' && (!j.retryAt || j.retryAt <= now))
       .sort((a, b) => a.createdAt - b.createdAt)[0];
 
     if (!next) {
@@ -98,7 +103,7 @@ async function processNextInLane(lane: string) {
     console.error(`[queue] Lane ${lane} processing error:`, err);
   } finally {
     const jobs = await listAllJobs();
-    const hasMore = jobs.some((j) => j.lane === lane && j.status === 'queued');
+    const hasMore = jobs.some((j) => j.lane === lane && j.status === 'queued' && (!j.retryAt || j.retryAt <= Date.now()));
     if (hasMore) {
       processNextInLane(lane);
     } else {
@@ -119,8 +124,10 @@ async function runJob(job: Job) {
 
   job.status = 'running';
   job.startedAt = Date.now();
+  job.retryAt = undefined;
   await writeJob(job);
-  console.log(`[queue] Running job ${job.id} (${job.type})`);
+  const isRetry = (job.retries ?? 0) > 0;
+  console.log(`[queue] ${isRetry ? 'Resuming' : 'Running'} job ${job.id} (${job.type})${isRetry ? ` retry ${job.retries}` : ''}`);
 
   const sharedMeta: Record<string, unknown> = { ...(job.meta ?? {}) };
 
@@ -134,6 +141,9 @@ async function runJob(job: Job) {
     const handlerStep = handler.steps[i]!;
     const step = fresh.steps[i]!;
 
+    // Skip already-completed steps on retry
+    if (step.status === 'completed') continue;
+
     fresh.currentStep = i;
     step.status = 'running';
     step.startedAt = Date.now();
@@ -171,9 +181,32 @@ async function runJob(job: Job) {
       step.status = 'failed';
       step.error = errorMessage;
       step.completedAt = Date.now();
+
+      // Check if handler supports retry
+      const retries = (fresh.retries ?? 0) + 1;
+      if (handler.retry && retries <= handler.retry.maxRetries) {
+        // Schedule retry: reset failed step to pending, re-queue
+        step.status = 'pending';
+        step.error = undefined;
+        step.startedAt = undefined;
+        step.completedAt = undefined;
+        step.progress = undefined;
+        fresh.status = 'queued';
+        fresh.error = undefined;
+        fresh.completedAt = undefined;
+        fresh.startedAt = undefined;
+        fresh.retries = retries;
+        fresh.retryAt = Date.now() + handler.retry.delayMs;
+        await writeJob(fresh);
+        console.log(`[queue] Job ${fresh.id} will retry (${retries}/${handler.retry.maxRetries}) in ${handler.retry.delayMs / 1000}s — failed at step "${step.name}": ${errorMessage}`);
+        scheduleRetry(fresh.lane, handler.retry.delayMs);
+        return;
+      }
+
       fresh.status = 'failed';
       fresh.error = `Step "${step.name}" failed: ${errorMessage}`;
       fresh.completedAt = Date.now();
+      fresh.meta = { ...fresh.meta, ...sharedMeta };
       await writeJob(fresh);
       console.error(`[queue] Job ${fresh.id} failed at step "${step.name}":`, errorMessage);
       if (fresh.notify !== false) await notifyFailure(fresh);