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/db.js

@@ -6,8 +6,8 @@ const pool = new Pool({
     user: process.env.PG_USER,
     password: process.env.PG_PASS,
     database: process.env.PG_DB,
-  // Ensure unqualified table names resolve to transit schema first.
-  options: '-c search_path=transit,public',
+  // Ensure unqualified table names resolve to the "transit.bus" schema first.
+  options: '-c search_path="transit.bus",public',
     max: 10,
     idleTimeoutMillis: 30000
 });
@@ -17,7 +17,26 @@ pool.query('SELECT 1')
   .catch(err => {
     console.error('PostgreSQL connection FAILED');
     console.error(err);
-    process.exit(1);
+    const url = process.env.ERROR_LOG_API_URL || 'https://error.xtransit.testinstance.nl/error_log';
+    const controller = new AbortController();
+    const timer = setTimeout(() => controller.abort(), 5000);
+    fetch(url, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/json',
+        'x-internal-api-key': process.env.INTERNAL_API_KEY || '',
+      },
+      body: JSON.stringify({
+        service: 'transit_api',
+        partofservice: 'startup: db connection',
+        error: err.stack || err.message || String(err),
+      }),
+      signal: controller.signal,
+    }).catch(() => {})
+      .finally(() => {
+        clearTimeout(timer);
+        process.exit(1);
+      });
   });
 
 module.exports = {