Decouple core Yaak logic from Tauri (#354)

crates/yaak-models/migrations/20250508161145_public-environments.sql

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+-- Add a public column to represent whether an environment can be shared or exported
+ALTER TABLE environments
+    ADD COLUMN public BOOLEAN DEFAULT FALSE;
+
+-- Add a base column to represent whether an environment is a base or sub environment. We used to
+-- do this with environment_id, but we need a more flexible solution now that envs can be optionally
+-- synced. E.g., it's now possible to only import a sub environment from a different client without
+-- its base environment "parent."
+ALTER TABLE environments
+    ADD COLUMN base BOOLEAN DEFAULT FALSE;
+
+-- SQLite doesn't support dynamic default values, so we update `base` based on the value of
+-- environment_id.
+UPDATE environments
+SET base = TRUE
+WHERE environment_id IS NULL;
+
+-- Finally, we drop the old `environment_id` column that will no longer be used
+ALTER TABLE environments
+    DROP COLUMN environment_id;