feat: index the text of attached PDFs

- jz_bm_material_file_texts caches the pdftotext output per file
- the River job jz.bm.extract_material_text extracts and resyncs
- the management multipart attach queues it inside its transaction
- file_texts in the document and a file snippet with its name

updates/20261108130000_create_jz_bm_material_file_texts.go

@@ -0,0 +1,34 @@
+package updates
+
+import (
+	"github.com/go-gormigrate/gormigrate/v2"
+	"gorm.io/gorm"
+)
+
+// CreateMaterialFileTexts returns the
+// 20261108130000_create_jz_bm_material_file_texts gormigrate entry: the text
+// pdftotext extracted from each PDF attached to a material, cached per file
+// so the search document can carry it without running the tool again. An
+// empty text means the file was extracted and held none (a scan or a broken
+// PDF), so it is not retried. The foreign key to system_files cascades, so
+// detaching a file removes its text; deleting a material removes the texts
+// of its files.
+func CreateMaterialFileTexts() *gormigrate.Migration {
+	return &gormigrate.Migration{
+		ID: "20261108130000_create_jz_bm_material_file_texts",
+		Migrate: func(tx *gorm.DB) error {
+			return execAll(tx, `
+CREATE TABLE jz_bm_material_file_texts (
+    file_id INTEGER PRIMARY KEY REFERENCES system_files (id) ON DELETE CASCADE,
+    material_id BIGINT NOT NULL REFERENCES jz_bm_materials (id) ON DELETE CASCADE,
+    text TEXT NOT NULL DEFAULT '',
+    truncated BOOLEAN NOT NULL DEFAULT FALSE,
+    extracted_at TIMESTAMP(0) WITHOUT TIME ZONE NOT NULL
+);
+CREATE INDEX jz_bm_material_file_texts_material_id_index ON jz_bm_material_file_texts (material_id)`)
+		},
+		Rollback: func(tx *gorm.DB) error {
+			return execAll(tx, `DROP TABLE IF EXISTS jz_bm_material_file_texts`)
+		},
+	}
+}