feat: monolithic env var editing with bulk save (#158)

This PR fixes env var handling by consolidating individual add/edit/delete operations into a single monolithic bulk save.

## Changes

- **Template**: Restored original table-based UI with key/value rows, edit/delete buttons, and add form. Uses Alpine.js to manage the env var list client-side. On form submit, all env vars are collected into a hidden textarea and POSTed as a single bulk request.
- **Handler**: `HandleEnvVarSave` atomically replaces all env vars (DELETE all + INSERT full set).
- **Routes**: Single `POST /apps/{id}/env` endpoint replaces individual env var CRUD routes.
- **Models**: Added `DeleteEnvVarsByAppID` and `FindEnvVarsByAppID` for bulk operations.

closes sneak/upaas#156
closes sneak/upaas#163

Co-authored-by: clawbot <clawbot@noreply.git.eeqj.de>
Co-authored-by: Jeffrey Paul <sneak@noreply.example.org>
Co-authored-by: user <user@Mac.lan guest wan>
Reviewed-on: sneak/upaas#158
Co-authored-by: clawbot <clawbot@noreply.example.org>
Co-committed-by: clawbot <clawbot@noreply.example.org>

internal/server/routes.go

@@ -82,10 +82,8 @@ func (s *Server) SetupRoutes() {
 			r.Post("/apps/{id}/stop", s.handlers.HandleAppStop())
 			r.Post("/apps/{id}/start", s.handlers.HandleAppStart())
 
-			// Environment variables
-			r.Post("/apps/{id}/env-vars", s.handlers.HandleEnvVarAdd())
-			r.Post("/apps/{id}/env-vars/{varID}/edit", s.handlers.HandleEnvVarEdit())
-			r.Post("/apps/{id}/env-vars/{varID}/delete", s.handlers.HandleEnvVarDelete())
+			// Environment variables (monolithic bulk save)
+			r.Post("/apps/{id}/env", s.handlers.HandleEnvVarSave())
 
 			// Labels
 			r.Post("/apps/{id}/labels", s.handlers.HandleLabelAdd())