Refactor transit_api into a repo/routes module split

Split the 5,441-line index.js into an 86-line bootstrap, thin domain
route modules, shared lib/ helpers, and a repo/ layer that isolates the
DEV_MOCK branches (repo/*.mock.js). Repo methods return {statusCode, body};
routes are one-line wrappers. Pin search_path to "transit.bus" and
document the /bus/ prefix with legacy root aliases (Deprecation header).

Parity verified: 57/57 byte-identical on the stub differential harness
plus 24/24 live read-only responses vs the original against real
PostgreSQL. The only intentional behavior change: mock reorder/delete
bus-line endpoints no longer require a live DB (previously 500 in
DEV_MOCK=1 without PG). DEV_MOCK gate and node --check clean.

transit_api/repo/fleet.js

@@ -0,0 +1,159 @@
+const db = require("../db");
+const { parseWeekdaysValue, checkBusConflict } = require("../lib/schedule");
+const { reportError } = require("../lib/report-error");
+
+// Fleet repository methods (PostgreSQL mode).
+
+async function listFleetBuses(req) {
+  try {
+    const result = await db.query(`
+      SELECT id, name, seat_capacity, license_plate
+      FROM fleet.bus
+      ORDER BY id ASC
+    `);
+
+    // Get all schedules to check for conflicts
+    const schedulesResult = await db.query(
+      `SELECT * FROM schedules WHERE status IN ('planned', 'active')`,
+    );
+    const schedules = schedulesResult.rows.map((row) => ({
+      ...row,
+      weekdays: parseWeekdaysValue(row.weekdays),
+    }));
+
+    return {
+      statusCode: 200,
+      body: {
+        buses: result.rows.map((row) => {
+          const busId = row.id;
+          const now = new Date();
+          const tomorrow = new Date(now);
+          tomorrow.setDate(tomorrow.getDate() + 1);
+          const isAvailable = !checkBusConflict(
+            busId,
+            now.toISOString(),
+            tomorrow.toISOString(),
+            [],
+            schedules,
+          );
+
+          return {
+            id: row.id,
+            name: row.name,
+            seatCapacity: row.seat_capacity,
+            licensePlate: row.license_plate,
+            available: isAvailable,
+          };
+        }),
+      },
+    };
+  } catch (err) {
+    console.error(err);
+    reportError({ partofservice: `${req.method} ${req.originalUrl}`, error: err.stack || err.message });
+    return { statusCode: 500, body: { error: "internal_error", details: err.message } };
+  }
+}
+
+async function createFleetBus(req) {
+  try {
+    const { name, seatCapacity, licensePlate } = req.body;
+
+    if (!name || seatCapacity === undefined || !licensePlate) {
+      return { statusCode: 400, body: { error: "missing_required_fields" } };
+    }
+
+    const result = await db.query(
+      `
+      WITH next_id AS (
+        SELECT COALESCE(MAX(id), 0) + 1 AS id FROM fleet.bus
+      )
+      INSERT INTO fleet.bus (id, name, seat_capacity, license_plate)
+      SELECT next_id.id, $1, $2, $3
+      FROM next_id
+      RETURNING id, name, seat_capacity, license_plate
+    `,
+      [name, seatCapacity, licensePlate],
+    );
+
+    const bus = result.rows[0];
+    return {
+      statusCode: 201,
+      body: {
+        bus: {
+          id: bus.id,
+          name: bus.name,
+          seatCapacity: bus.seat_capacity,
+          licensePlate: bus.license_plate,
+        },
+      },
+    };
+  } catch (err) {
+    console.error(err);
+    reportError({ partofservice: `${req.method} ${req.originalUrl}`, error: err.stack || err.message });
+    return { statusCode: 500, body: { error: "internal_error", details: err.message } };
+  }
+}
+
+async function updateFleetBus(req) {
+  try {
+    const { busId } = req.params;
+    const { name, seatCapacity, licensePlate } = req.body;
+
+    if (!busId || !Number.isFinite(Number(busId))) {
+      return { statusCode: 400, body: { error: "invalid_bus_id" } };
+    }
+
+    const result = await db.query(
+      `
+      UPDATE fleet.bus
+      SET name = COALESCE($1, name), seat_capacity = COALESCE($2, seat_capacity), license_plate = COALESCE($3, license_plate), updated_at = NOW()
+      WHERE id = $4
+      RETURNING id, name, seat_capacity, license_plate
+    `,
+      [name ?? null, seatCapacity ?? null, licensePlate ?? null, busId],
+    );
+
+    if (!result.rows[0])
+      return { statusCode: 404, body: { error: "bus_not_found" } };
+
+    const bus = result.rows[0];
+    return {
+      statusCode: 200,
+      body: {
+        bus: {
+          id: bus.id,
+          name: bus.name,
+          seatCapacity: bus.seat_capacity,
+          licensePlate: bus.license_plate,
+        },
+      },
+    };
+  } catch (err) {
+    console.error(err);
+    reportError({ partofservice: `${req.method} ${req.originalUrl}`, error: err.stack || err.message });
+    return { statusCode: 500, body: { error: "internal_error", details: err.message } };
+  }
+}
+
+async function deleteFleetBus(req) {
+  try {
+    const { busId } = req.params;
+    if (!busId || !Number.isFinite(Number(busId))) {
+      return { statusCode: 400, body: { error: "invalid_bus_id" } };
+    }
+
+    const result = await db.query(
+      `DELETE FROM fleet.bus WHERE id = $1 RETURNING id, name`,
+      [busId],
+    );
+    if (result.rows.length === 0)
+      return { statusCode: 404, body: { error: "bus_not_found" } };
+    return { statusCode: 200, body: { success: true, bus: result.rows[0] } };
+  } catch (err) {
+    console.error(err);
+    reportError({ partofservice: `${req.method} ${req.originalUrl}`, error: err.stack || err.message });
+    return { statusCode: 500, body: { error: "internal_error", details: err.message } };
+  }
+}
+
+module.exports = { listFleetBuses, createFleetBus, updateFleetBus, deleteFleetBus };