feat: add Area and InventoryScan Prisma models + migrations

Office-move inventory kiem ke feature. See docs/asset-license-management.md InventoryScan section for full business rationale (Area vs Seat, why not AssetItem, asset tag/serial nullable).

Co-Authored-By: Claude Sonnet 5 <[email protected]>

prisma/schema.prisma

@@ -74,6 +74,11 @@ model Employee {
   // Assignments (assets/licenses) over time, including several active ones
   // at once (e.g. a laptop + a license seat simultaneously).
   assignments            Assignment[]
+  // Back-relation for InventoryScan.assignedEmployeeId — see InventoryScan's
+  // comment. An Employee can have multiple scanned items (workstation +
+  // monitor + controller, etc.) attributed to them from the office-move
+  // inventory walk.
+  inventoryScans         InventoryScan[]
   createdAt              DateTime        @default(now()) @map("created_at") @db.Timestamptz(6)
 
   @@map("employees")
@@ -280,6 +285,8 @@ model AssetCategory {
   // not expressible as a Prisma-level constraint), but the relation itself
   // is not restricted to high_value categories at the schema level.
   assetModels   AssetModel[]
+  // Back-relation for InventoryScan.categoryId — see InventoryScan's comment.
+  inventoryScans InventoryScan[]
 
   @@map("asset_categories")
 }
@@ -361,6 +368,8 @@ model AssetModel {
   // Back-relation for the AssetItem.model -> AssetItem.modelId retrofit —
   // see "Cập nhật 2026-08-02 (2)" in docs/asset-license-management.md.
   assetItems   AssetItem[]
+  // Back-relation for InventoryScan.modelId — see InventoryScan's comment.
+  inventoryScans InventoryScan[]
 
   @@map("asset_models")
 }
@@ -473,3 +482,89 @@ model MaintenanceRecord {
 
   @@map("maintenance_records")
 }
+
+// Physical location tag for the office-move inventory walk — see the
+// "chia theo area" decision in the inventory-scans project chat. Deliberately
+// NOT the pre-existing high-value AssetItem's target ("Seat" tied 1:1 to a
+// Employee/team) because that data (the new office seating chart) doesn't
+// exist yet at the time this was built — `team` is nullable and gets filled
+// in once the seating chart is finalized, no schema change needed then.
+// Covers both per-seat locations ("Seat 12") and shared-room locations
+// ("Phòng họp A", "Kho tầng 2") with the same flat entity — splitting seat
+// vs room into separate types was considered and rejected as premature; add
+// a `type` column later if filtering by kind actually becomes necessary.
+// `name` is globally unique so the bot's "reuse existing or create new" flow
+// (grows the list as the walk progresses, avoids duplicate near-identical
+// area names from free-typing) has something to match against.
+model Area {
+  id             String          @id @default(uuid()) @db.Uuid
+  name           String          @unique
+  team           String?
+  createdAt      DateTime        @default(now()) @map("created_at") @db.Timestamptz(6)
+  inventoryScans InventoryScan[]
+
+  @@map("areas")
+}
+
+// One physical item logged during the office-move inventory walk (bot flow:
+// Category -> Model -> [Workstation only: cpu/ram/gpu] -> Area -> assignee ->
+// optional photo). Deliberately NOT a row in AssetItem: AssetItem requires a
+// unique serialNumber and a purchaseDate, neither of which is known/at-hand
+// during a fast walk-and-tap pass — forcing either would either block the
+// walk or invent fake placeholder data, which this codebase avoids elsewhere
+// (see AssetItem/License/PurchaseOrder comments' "no fake data" precedent).
+// InventoryScan is the lightweight capture; promoting a scan to a real
+// AssetItem (with a real serial once read off the physical tag) is a manual
+// follow-up step done later in the review UI, not built in this task.
+// `categoryId`/`modelId` reuse the existing AssetCategory/AssetModel catalog
+// (seeded with Controller/Màn hình/Workstation for this task's scope) rather
+// than inventing a parallel classification. `areaId` and `assignedEmployeeId`
+// are both nullable — plenty of scanned items are shared equipment in a room
+// (no single assignee) or not yet placed in a known Area. `specs` is JSONB,
+// same shape/rationale as AssetModel.specs — holds the Workstation-only
+// cpu/ram/gpu answers; empty object for categories that don't need them.
+// `telegramChatId`/`telegramMessageId` are kept for traceability back to the
+// original bot conversation (debugging a bad scan, or re-fetching the photo
+// from Telegram if `photoPath` is ever lost) — nullable since a scan created
+// directly from the review UI later won't have either.
+model InventoryScan {
+  id                 String         @id @default(uuid()) @db.Uuid
+  categoryId         String         @map("category_id") @db.Uuid
+  category           AssetCategory  @relation(fields: [categoryId], references: [id])
+  modelId            String         @map("model_id") @db.Uuid
+  model              AssetModel     @relation(fields: [modelId], references: [id])
+  areaId             String?        @map("area_id") @db.Uuid
+  area               Area?          @relation(fields: [areaId], references: [id])
+  assignedEmployeeId String?        @map("assigned_employee_id") @db.Uuid
+  assignedEmployee   Employee?      @relation(fields: [assignedEmployeeId], references: [id])
+  // Physical asset tag/barcode label already stuck on the device (see the
+  // "Scan QR/barcode đã có sẵn trên thiết bị" scope decision). Free text,
+  // typed by the bot operator for now — not yet an actual barcode-image
+  // decode. Deliberately NOT unique/required at this table's level (unlike
+  // AssetItem.serialNumber): plenty of scanned items have no tag at all
+  // (Controllers, Monitors bought without one), and enforcing uniqueness
+  // here would block the walk on a typo'd re-entry instead of just letting
+  // review-time cleanup catch it, per this model's "don't block the walk"
+  // precedent (see AssetItem-vs-InventoryScan comment above).
+  assetTag           String?        @map("asset_tag")
+  // Manufacturer serial number, read off the same physical tag as
+  // assetTag — same "don't block the walk" rationale (nullable, not
+  // unique at this table's level; AssetItem.serialNumber is the unique
+  // one, enforced only once a scan is promoted). Filled in either by
+  // typing, or later by whoever reviews the scan's photo (bot operator or
+  // Claude) reading it off the image — no OCR automation built yet, this
+  // column is just where that value lands once read.
+  serialNumber       String?        @map("serial_number")
+  specs              Json           @default("{}")
+  // Stores the Telegram file_id (not a local disk path, despite the DB
+  // column name) — photos live on Telegram's servers, re-fetched on demand
+  // via GET /api/inventory-scans/[id]/photo rather than duplicated onto
+  // this app's own disk. Avoids a shared volume mount between this
+  // container and the separate inventory-capture bot service.
+  photoFileId        String?        @map("photo_path")
+  telegramChatId     String?        @map("telegram_chat_id")
+  telegramMessageId  Int?           @map("telegram_message_id")
+  createdAt          DateTime       @default(now()) @map("created_at") @db.Timestamptz(6)
+
+  @@map("inventory_scans")
+}