feat(TRUEREF-0022): complete iteration 0 — worker-thread indexing, parallel jobs, SSE progress

- Move IndexingPipeline.run() into Worker Threads via WorkerPool
- Add dedicated embedding worker thread with single model instance
- Add stage/stageDetail columns to indexing_jobs schema
- Create ProgressBroadcaster for SSE channel management
- Add SSE endpoints: GET /api/v1/jobs/:id/stream, GET /api/v1/jobs/stream
- Replace UI polling with EventSource on repo detail and admin pages
- Add concurrency settings UI and API endpoint
- Build worker entries separately via esbuild

src/lib/server/db/migrations/meta/_journal.json

@@ -1,34 +1,41 @@
 {
-	"version": "7",
-	"dialect": "sqlite",
-	"entries": [
-		{
-			"idx": 0,
-			"version": "6",
-			"when": 1774196053634,
-			"tag": "0000_large_master_chief",
-			"breakpoints": true
-		},
-		{
-			"idx": 1,
-			"version": "6",
-			"when": 1774448049161,
-			"tag": "0001_quick_nighthawk",
-			"breakpoints": true
-		},
-		{
-			"idx": 2,
-			"version": "6",
-			"when": 1774461897742,
-			"tag": "0002_silky_stellaris",
-			"breakpoints": true
-		},
-		{
-			"idx": 3,
-			"version": "6",
-			"when": 1743155877000,
-			"tag": "0003_multiversion_config",
-			"breakpoints": true
-		}
-	]
-}
+  "version": "7",
+  "dialect": "sqlite",
+  "entries": [
+    {
+      "idx": 0,
+      "version": "6",
+      "when": 1774196053634,
+      "tag": "0000_large_master_chief",
+      "breakpoints": true
+    },
+    {
+      "idx": 1,
+      "version": "6",
+      "when": 1774448049161,
+      "tag": "0001_quick_nighthawk",
+      "breakpoints": true
+    },
+    {
+      "idx": 2,
+      "version": "6",
+      "when": 1774461897742,
+      "tag": "0002_silky_stellaris",
+      "breakpoints": true
+    },
+    {
+      "idx": 3,
+      "version": "6",
+      "when": 1743155877000,
+      "tag": "0003_multiversion_config",
+      "breakpoints": true
+    },
+    {
+      "idx": 4,
+      "version": "6",
+      "when": 1774880275833,
+      "tag": "0004_complete_sentry",
+      "breakpoints": true
+    }
+  ]
+}