feat: add basic auth middleware UI under Traefik Dynamic

[quochuydev]

Lets users create and delete Traefik basicAuth middlewares from the Traefik dashboard, so compose services can reference them as <name>@file via labels without hand-editing middlewares.yml.

What is this PR about?

Adds a Basic Auth Middlewares card to the Traefik dashboard page (/dashboard/traefik) that lets users create and delete Traefik basicAuth middlewares directly in middlewares.yml from the UI.

Today, Applications can manage basic auth via Advanced → Security, but Compose apps (and anyone wanting a standalone basic auth middleware) have to SSH into the host and hand-edit YAML plus bcrypt hashes. This PR closes that gap with a generic, app-agnostic middleware manager.

The generated middleware is referenced manually as <name>@file — either in compose labels or in a domain's Middlewares field — followed by a user-initiated redeploy. Traefik picks up the YAML change live.

Checklist

Before submitting this PR, please make sure that:

• I created a dedicated branch based on the canary branch (feat/traefik-basic-auth-middleware-ui).
• I have read the suggestions in the CONTRIBUTING.md file.
• I have tested this PR in my local instance.

Issues related (if applicable)

closes #4284

Screenshots (if applicable)

Greptile Summary

This PR adds a Basic Auth Middlewares UI to the Traefik dashboard, letting users create and delete basicAuth entries in middlewares.yml without hand-editing YAML. The approach is consistent with how the rest of the codebase manages Traefik dynamic config.

• P1 — null-config crash: loadMiddlewares() returns null for an empty middlewares.yml (no exception is thrown, so the catch is bypassed). Both createBasicAuthMiddleware and deleteBasicAuthMiddleware then dereference that null value without guarding against it, causing an unhandled TypeError on the server.

Confidence Score: 4/5

Safe to merge after fixing the null-config crash in the two new mutations.

One P1 defect: both mutating endpoints crash with a TypeError if middlewares.yml exists but is empty, because loadMiddlewares() returns null without throwing. The rest of the implementation follows existing codebase patterns and introduces no security regressions.

apps/dokploy/server/api/routers/settings.ts — null guard after loadMiddlewares() in both createBasicAuthMiddleware and deleteBasicAuthMiddleware

_{Reviews (1): Last reviewed commit: "[autofix.ci] apply automated fixes" | Re-trigger Greptile}

Greptile also left 2 inline comments on this PR.