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/migrations/20260714130000_locator_telemetry/migration.sql

@@ -0,0 +1,25 @@
+-- Locator receiver telemetry + device identity by serial number.
+-- NOTE: hand-edited — Prisma's diff wanted to drop the geom GIST index and the
+-- generated-column expression on locate_points.geom; those statements were removed.
+
+-- CreateEnum
+CREATE TYPE "LocateMode" AS ENUM ('PEAK', 'NULL', 'BROAD_PEAK', 'SONDE');
+
+-- AlterTable
+ALTER TABLE "devices" ALTER COLUMN "mqttUsername" DROP NOT NULL;
+
+-- AlterTable
+ALTER TABLE "locate_points" ADD COLUMN     "compassDeg" DECIMAL(5,2),
+ADD COLUMN     "currentMa" DECIMAL(9,3),
+ADD COLUMN     "distortionPct" DECIMAL(5,2),
+ADD COLUMN     "frequencyHz" INTEGER,
+ADD COLUMN     "gainDb" DECIMAL(6,2),
+ADD COLUMN     "hdop" DECIMAL(4,2),
+ADD COLUMN     "locateMode" "LocateMode",
+ADD COLUMN     "phaseDeg" DECIMAL(6,2),
+ADD COLUMN     "satellites" INTEGER,
+ADD COLUMN     "signalDb" DECIMAL(6,2),
+ADD COLUMN     "vAccuracy" DECIMAL(7,3);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "devices_orgId_serialNumber_key" ON "devices"("orgId", "serialNumber");