feat(server,app,website): prefix service URLs with project slug

Service hostnames now follow DNS convention with a project label so
independently opened projects no longer collide on routes like
`web.localhost`. Format becomes `{script}.{project}.localhost` for
default branches and `{script}.{branch}.{project}.localhost` for other
branches. The project slug comes from the GitHub repository name when a
remote exists, otherwise from the workspace directory basename.

Server changes:
- `buildScriptHostname` takes `{ projectSlug, branchName, scriptName }`
  and slugifies all labels at the boundary; `untitled` fallback only
  applies at hostname-label sites, never to shared `slugify`.
- `deriveProjectSlug(cwd)` and `parseGitHubRepoNameFromRemote` derive
  the slug; GitHub URL parsing now requires `host === "github.com"` to
  avoid embedded-path false matches.
- `ScriptRouteEntry` carries `projectSlug`; branch-rename handler reuses
  it instead of re-reading git in hot paths.
- Status projection derives slug once per call and uses route hostname
  when available; only falls back to building when no route exists.
- Spawn cleanup removes routes by `{ workspaceId, scriptName }` so
  cleanup after a branch rename doesn't leave a stale entry behind.

App and shared message tests updated to the new fixture shape; service
URLs continue to be opaque server-provided strings.

Landing-page service URL examples updated; allowlist docs unchanged.

packages/app/src/contexts/session-context.service-status.test.ts

@@ -26,9 +26,9 @@ function workspace(input: {
 const runningScript: WorkspaceScriptPayload = {
   scriptName: "web",
   type: "service",
-  hostname: "main.web.localhost",
+  hostname: "web.paseo.localhost",
   port: 3000,
-  proxyUrl: "http://main.web.localhost:6767",
+  proxyUrl: "http://web.paseo.localhost:6767",
   lifecycle: "running",
   health: "healthy",
   exitCode: null,