fix: Enhance Kol Variable Rendering and Management

- Updated the regex for placeholder matching to support more flexible key formats.
- Refactored variable storage to allow both ID and key lookups in rendering.
- Improved schema validation to check for duplicate keys and enforce non-empty keys.
- Added new utility functions for variable value lookup and display name generation.
- Enhanced tests to cover new key-based variable scenarios.
- Refactored KolPrompt repository to simplify prompt storage and management, including the removal of obsolete revision handling.
- Introduced new API endpoints for saving, activating, and archiving prompts.
- Added new utility functions for handling Kol placeholders and platform options in the admin web.
- Implemented database migrations to simplify prompt storage structure and ensure data integrity.

server/migrations/20260418110000_simplify_kol_prompt_storage.down.sql

@@ -0,0 +1,12 @@
+ALTER TABLE kol_usage_logs
+    DROP CONSTRAINT IF EXISTS fk_kol_usage_logs_prompt_revision;
+
+ALTER TABLE kol_usage_logs
+    ADD CONSTRAINT fk_kol_usage_logs_prompt_revision
+    FOREIGN KEY (prompt_id, prompt_revision_no)
+    REFERENCES kol_prompt_revisions(prompt_id, revision_no);
+
+ALTER TABLE kol_prompts
+    DROP COLUMN IF EXISTS card_config_json,
+    DROP COLUMN IF EXISTS schema_json,
+    DROP COLUMN IF EXISTS prompt_asset_key;