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/drivers.js

@@ -0,0 +1,88 @@
+const db = require("../db");
+const { parseWeekdaysValue, checkDriverConflict } = require("../lib/schedule");
+const { reportError } = require("../lib/report-error");
+
+// Driver repository methods (PostgreSQL mode).
+
+async function listDrivers(req) {
+  try {
+    const result = await db.query(`
+      SELECT id, firstname, lastname, email, phone, job, joined, status
+      FROM workers.employees
+      WHERE status = 'active'
+      ORDER BY firstname, lastname 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: {
+        drivers: result.rows.map((row) => {
+          const driverId = row.id;
+          const now = new Date();
+          const tomorrow = new Date(now);
+          tomorrow.setDate(tomorrow.getDate() + 1);
+          const isAvailable = !checkDriverConflict(
+            driverId,
+            now.toISOString(),
+            tomorrow.toISOString(),
+            [],
+            schedules,
+          );
+
+          return {
+            id: row.id,
+            name: (
+              String(row.firstname || "") +
+              " " +
+              String(row.lastname || "")
+            ).trim(),
+            email: row.email,
+            phone: row.phone,
+            job: row.job,
+            joined: row.joined,
+            status: row.status,
+            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 listShiftDrivers(req) {
+  try {
+    const result = await db.query(`
+      SELECT id, usercode
+      FROM workers.users
+      ORDER BY usercode ASC
+    `);
+    return {
+      statusCode: 200,
+      body: {
+        drivers: result.rows.map((row) => ({
+          id: Number(row.id),
+          name: String(row.usercode),
+        })),
+      },
+    };
+  } catch (err) {
+    console.error("GET /admin/shift-drivers error:", err);
+    reportError({ partofservice: "GET /admin/shift-drivers", error: err.stack || err.message });
+    return { statusCode: 500, body: { error: "internal_error" } };
+  }
+}
+
+module.exports = { listDrivers, listShiftDrivers };