feat: add deep research planning and postal batch runs

Add a dedicated Deep Research view with postal-area preview overlays, batch execution, and bundled map results.

Also add postal dataset import tooling and fix local API networking and research insert issues needed to support the new workflow.

db/datasets/README.md

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+# Postal Datasets
+
+Leads4less expects local GeoJSON files for deep research postal overlays.
+
+## Supported v1 datasets
+
+- US ZIP/ZCTA polygons
+- Canada FSA polygons
+
+## Default file locations
+
+- `db/datasets/postal/us_zcta.geojson`
+- `db/datasets/postal/ca_fsa.geojson`
+
+You can override either path with environment variables when running the import script:
+
+- `POSTAL_US_DATASET_PATH`
+- `POSTAL_CA_DATASET_PATH`
+
+## Expected feature properties
+
+The importer tries common field names automatically.
+
+For US ZIP/ZCTA:
+- `postal_code`
+- `zip`
+- `zcta`
+- `GEOID20`
+- `ZCTA5CE20`
+- `ZCTA5CE10`
+
+For Canada FSA:
+- `postal_code`
+- `fsa`
+- `CFSAUID`
+- `CFSAUID24`
+
+If your dataset uses different property names, update `db/scripts/import-postal-areas.ts`.