chore: migrate from environment_namespace to environment_id

[cre8ivejp]

As part of the Organization feature, we must migrate to environment_id soon to avoid future bugs and conflicts.

We will replace the environment_namespace column with the environment_id column for all tables; this PR will first add the environment_id column.

Here is the migration process:

1. Add a new column
   Add the environment_id column to all relevant tables, allowing NULL initially

   ALTER TABLE `table_name` ADD COLUMN `environment_id` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NULL;

2. Populate a new column
   Populate the new environment_id column with data from environment_namespace:

   UPDATE `table_name` SET `environment_id` = `environment_namespace`;

3. Update backend service (Phase 1)
   Update service to write to both environment_namespace and environment_id columns. Read primarily from environment_id, falling back to environment_namespace if environment_id is NULL. This ensures compatibility with both old and new data.

4. Backfill any missing data
   If any data was written during the deployment of the updated service:

   UPDATE `table_name` SET `environment_id` = `environment_namespace` WHERE `environment_id` IS NULL;

5. Make new column NOT NULL
   After verifying all data is populated:

   ALTER TABLE `table_name` MODIFY COLUMN `environment_id` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin NOT NULL;

6. Update backend service (Phase 2)
   Update service to only write to and read from environment_id. Remove all references to environment_namespace.