refactor: replace v2 live migration with regular SQL migration (#7678)

* refactor: replace v2 live migration with regular SQL migration

Remove the v2_finalize live migration that waited for workers to reach
v1.461+ and replace it with an idempotent SQL migration. Since enough
time has passed, all deployments are assumed to be on v1.461+.

Changes:
- Remove v2_finalize() function and spawn task from live_migrations.rs
- Remove MIN_VERSION_IS_AT_LEAST_1_461 constant from min_version.rs
- Add 20260125000000_v2_finalize.up.sql with all finalization steps
- All SQL operations use IF EXISTS/CASCADE for idempotency

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* refactor: remove migration-related delays and tighten CLI tests CI trigger

- Remove 5s backend initialization delay in cargo_backend.ts that was
  needed for the v2 live migration (now replaced with SQL migration)
- Restrict CLI tests workflow to only trigger on cli/** changes
  (removed backend/**, openapi.yaml, openflow.openapi.yaml paths)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: skip v2_finalize migration if live migration already ran

Wrap migration in DO block that checks for 'v2_finalize_job_completed'
in windmill_migrations table. If present (live migration already ran),
skip entirely to avoid unnecessary table locks on upgraded instances.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

cli/test/cargo_backend.ts

@@ -160,11 +160,6 @@ export class CargoBackend {
     console.log(`   Server: ${this.baseUrl}`);
     console.log(`   Database: ${this.dbName}`);
     console.log(`   Workspace: ${this.config.workspace}`);
-
-    // Wait for backend to fully initialize (migrations, etc.)
-    console.log("⏳ Waiting 5s for backend to fully initialize...");
-    await new Promise(resolve => setTimeout(resolve, 5000));
-    console.log("✅ Ready to run tests");
   }
 
   /**