feat: add app status tracking to the backend (#17163)

This does ~95% of the backend work required to integrate the AI work.

Most left to integrate from the tasks branch is just frontend, which
will be a lot smaller I believe.

The real difference between this branch and that one is the abstraction
-- this now attaches statuses to apps, and returns the latest status
reported as part of a workspace.

This change enables us to have a similar UX to in the tasks branch, but
for agents other than Claude Code as well. Any app can report status
now.

coderd/database/migrations/testdata/fixtures/000313_workspace_app_statuses.up.sql

@@ -0,0 +1,19 @@
+INSERT INTO workspace_app_statuses (
+    id,
+    created_at,
+    agent_id,
+    app_id,
+    workspace_id,
+    state,
+    needs_user_attention,
+    message
+) VALUES (
+    gen_random_uuid(),
+    NOW(),
+    '7a1ce5f8-8d00-431c-ad1b-97a846512804',
+	'36b65d0c-042b-4653-863a-655ee739861c',
+	'3a9a1feb-e89d-457c-9d53-ac751b198ebe',
+    'working',
+    false,
+    'Creating SQL queries for test data!'
+);