feat(seo): generate slugs for brands, categories and products, add GET /sitemap and the Postman collection (#5)

postman/collections/DinggaDingga/syncHiboutik.request.yaml

@@ -0,0 +1,26 @@
+$kind: http-request
+description: |-
+  Starts a full Hiboutik → database synchronization **in the background** and answers immediately: the request never waits for the sync to end.
+
+  **What it syncs**, in dependency order: brands → categories → suppliers → products (with their versions and stocks) → customers (with their addresses and orders). New brands, categories and products get their slug at the end of their step.
+
+  **Hiboutik is the source of truth**: brands, categories, suppliers, products and customers missing from Hiboutik are deleted from the database (orders are never deleted). A failed Hiboutik call deletes nothing. A failing item is logged and skipped; the sync goes on and logs a summary at the end. Follow its progress in the server logs.
+
+  **One sync at a time**, across all instances (Postgres advisory lock): a call while a sync is running answers `409`.
+
+  **Cost**: a sync uses roughly one Hiboutik API call per customer, plus a few per entity type. Hiboutik allows 10,000 calls per month per shop; when its rate limit is reached, the sync stops.
+
+  **Responses**
+  - `202` sync started.
+  - `409` a sync is already running (on this instance or another one).
+  - `429` rate limit: 5 calls per minute per IP on this route. `Retry-After` gives the seconds to wait.
+  - `503` this instance is shutting down: retry, another instance can take the call.
+  - `500` unexpected error (e.g. database unreachable); details are in the server logs only.
+
+  No body, no parameters.
+url: "{{baseUrl}}/sync"
+method: POST
+headers:
+  Accept: application/json
+examples: ./.resources/syncHiboutik.resources/examples
+order: 1000