fix(server): use axum 0.7 path syntax for :id route params (recording/model delete 404s)

[fallen-pc]

Problem

DELETE /api/v1/recording/{id} and DELETE /api/v1/models/{id} return 404 for every id. In the dashboard this shows up as recording deletion in the Training tab silently failing.

The routes are declared with {id}:

.route("/api/v1/models/{id}",    delete(delete_model))
.route("/api/v1/recording/{id}", delete(delete_recording))

{param} is the axum 0.8 / matchit 0.8 capture syntax. The workspace pins axum = "0.7" (0.7.9 in Cargo.lock), where captures are :param and {id} is matched as a literal path segment. So no real id ever matches, the request falls through to the 404 fallback, and the handlers are never reached.

Corroborating detail: neither handler is capable of returning 404 - both return Json<serde_json::Value>, i.e. HTTP 200 with an error body:

Json(serde_json::json!({ "error": "recording not found", "success": false }))

so a bare 404 can only mean the route did not match.

Fix

{id} -> :id in five route declarations:

• main.rs - /api/v1/models/{id}, /api/v1/recording/{id} (both live)
• model_manager.rs - /api/v1/models/{id}
• recording.rs - /api/v1/recording/download/{id}, /api/v1/recording/{id}

The latter three are in routers not currently merged into the app, corrected for consistency so they don't reintroduce the bug if they're mounted later.

The format!("/api/v1/sites/{site_id}/...") strings in vendor_mist_netgear.rs are deliberately untouched - those are Rust format interpolation building outbound URLs, not axum routes.

Verification

Built and run locally, --source esp32:

Request	Before	After
DELETE /api/v1/recording/does-not-exist-test	404 (empty)	200 {"error":"recording not found","success":false}
GET /api/v1/models/<id>	404	405 (path matches, method not registered on the live router)

cargo build -p wifi-densepose-sensing-server clean.

Note

If the project intends to move to axum 0.8, the inverse change would be needed across the whole crate - this PR aligns the routes with the version currently pinned, which is the smaller and safer of the two.