Tie points to locator serial numbers and store receiver telemetry

Field setups often relay through a phone/gateway that owns the MQTT
connection, so the publishing credential and the instrument are now
separate concepts:

- Points messages carry a "serial" identifying the locator receiver;
  unknown serials are auto-registered as devices in the publisher's
  org (name "Locator <serial>"). Device.mqttUsername is now optional
  and serialNumber is unique per org.
- LocatePoint gains standard receiver telemetry: frequencyHz,
  currentMa, signalDb, gainDb, locateMode (PEAK/NULL/BROAD_PEAK/SONDE),
  phaseDeg, compassDeg, distortionPct, plus GPS quality columns
  vAccuracy, satellites, hdop. All optional; raw payload still kept.
- Migration hand-edited to preserve the generated geom column and its
  GIST index (Prisma diff wanted to drop both).
- REST create/point DTOs, map tooltips, job-detail latest-point
  readout, devices settings form, seed, and the sample publisher all
  carry the new fields.
- Added .dockerignore for backend/web: COPY . . was clobbering the
  image's freshly generated Prisma client with the host's stale
  node_modules, breaking image builds after schema changes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/prisma/schema.prisma

@@ -45,6 +45,14 @@ enum GpsFixType {
   FIXED_RTK
 }
 
+// EM locator receiver antenna mode used when the point was captured
+enum LocateMode {
+  PEAK
+  NULL
+  BROAD_PEAK
+  SONDE
+}
+
 model Organization {
   id          String          @id @default(cuid())
   name        String
@@ -116,12 +124,16 @@ model Job {
   @@map("jobs")
 }
 
+// A device is either a locator receiver (identified by serialNumber, usually
+// auto-registered from incoming data) or an MQTT publisher (app/gateway with
+// broker credentials, identified by mqttUsername) — or both, when a locator
+// connects to the broker directly.
 model Device {
   id           String    @id @default(cuid())
   orgId        String
   name         String
   serialNumber String?
-  mqttUsername String    @unique
+  mqttUsername String?   @unique
   isActive     Boolean   @default(true)
   lastSeenAt   DateTime? @db.Timestamptz(6)
   createdAt    DateTime  @default(now()) @db.Timestamptz(6)
@@ -130,6 +142,7 @@ model Device {
   org    Organization  @relation(fields: [orgId], references: [id], onDelete: Cascade)
   points LocatePoint[]
 
+  @@unique([orgId, serialNumber])
   @@map("devices")
 }
 
@@ -140,15 +153,31 @@ model LocatePoint {
   lat         Decimal     @db.Decimal(10, 8)
   lng         Decimal     @db.Decimal(11, 8)
   altitude    Decimal?    @db.Decimal(8, 3)
-  fixType     GpsFixType  @default(NONE)
-  hAccuracy   Decimal?    @db.Decimal(7, 3)
-  depth       Decimal?    @db.Decimal(6, 3)
   utilityType UtilityType @default(UNKNOWN)
   sequence    Int?
-  recordedAt  DateTime    @db.Timestamptz(6)
-  receivedAt  DateTime    @default(now()) @db.Timestamptz(6)
-  raw         Json?
-  geom        Unsupported("geometry(Point, 4326)")?
+
+  // GPS quality
+  fixType    GpsFixType @default(NONE)
+  hAccuracy  Decimal?   @db.Decimal(7, 3) // meters
+  vAccuracy  Decimal?   @db.Decimal(7, 3) // meters
+  satellites Int?
+  hdop       Decimal?   @db.Decimal(4, 2)
+
+  // Locator receiver telemetry
+  depth         Decimal?    @db.Decimal(6, 3) // meters below grade
+  frequencyHz   Int? // active/passive locate frequency
+  currentMa     Decimal?    @db.Decimal(9, 3) // signal current on the line
+  signalDb      Decimal?    @db.Decimal(6, 2) // signal strength
+  gainDb        Decimal?    @db.Decimal(6, 2) // receiver gain
+  locateMode    LocateMode?
+  phaseDeg      Decimal?    @db.Decimal(6, 2)
+  compassDeg    Decimal?    @db.Decimal(5, 2) // line direction, 0-360
+  distortionPct Decimal?    @db.Decimal(5, 2)
+
+  recordedAt DateTime @db.Timestamptz(6)
+  receivedAt DateTime @default(now()) @db.Timestamptz(6)
+  raw        Json?
+  geom       Unsupported("geometry(Point, 4326)")?
 
   job    Job     @relation(fields: [jobId], references: [id], onDelete: Cascade)
   device Device? @relation(fields: [deviceId], references: [id], onDelete: SetNull)