wip(intake): router, enrich endpoint, Slack handlers, migration 0034 — UNTESTED checkpoint

Agent was terminated by the session usage limit before running lint/tests or
writing its report. Files are complete drafts against plan §11 (C1, C2, C5):
src/app/api/intake/, src/app/api/transactions/[id]/line-items/, src/lib/intake-*.ts,
src/lib/line-items.ts, prisma/migrations/0034_intake_batches, fixtures + tests.
Next: npm ci && npx prisma generate && npm run lint && npm test && npm run test:integration.

package-lock.json

@@ -16,7 +16,8 @@
         "prisma": "^7.4.2",
         "react": "19.2.3",
         "react-dom": "19.2.3",
-        "recharts": "^3.8.0"
+        "recharts": "^3.8.0",
+        "unpdf": "^1.8.1"
       },
       "devDependencies": {
         "@tailwindcss/postcss": "^4",
@@ -8494,6 +8495,23 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/unpdf": {
+      "version": "1.8.1",
+      "resolved": "https://registry.npmjs.org/unpdf/-/unpdf-1.8.1.tgz",
+      "integrity": "sha512-xkURhy2SoGpOIH0a1gLHNkASPIQYonadDJs2AQwPEfUakafeD9EA1WTWWsaR++gfTCXJpV27W7tU1nXuk82UKQ==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=22"
+      },
+      "peerDependencies": {
+        "@napi-rs/canvas": "^0.1.69 || ^1.0.0"
+      },
+      "peerDependenciesMeta": {
+        "@napi-rs/canvas": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/unrs-resolver": {
       "version": "1.11.1",
       "resolved": "https://registry.npmjs.org/unrs-resolver/-/unrs-resolver-1.11.1.tgz",