feat: Refactor user and thought models to use UUIDs instead of integers

- Updated user and thought models to utilize UUIDs for primary keys.
- Modified persistence functions to accommodate UUIDs for user and thought IDs.
- Implemented tag functionality with new Tag and ThoughtTag models.
- Added migration scripts to create new tables for tags and thought-tag relationships.
- Enhanced thought creation to parse hashtags and link them to thoughts.
- Updated tests to reflect changes in user and thought ID types.

thoughts-backend/utils/Cargo.toml

@@ -10,7 +10,7 @@ path = "src/lib.rs"
 
 [dependencies]
 migration = { path = "../migration" }
-uuid = { version = "1.18.1", features = ["v4"] }
+uuid = { version = "1.18.1", features = ["v4", "serde"] }
 sea-orm = { version = "1.1.12", features = ["sqlx-sqlite", "sqlx-postgres"] }
 
 axum = { workspace = true }