Refactor blog module and remove blog-related functionality

- Removed blog router and associated API endpoints.
- Deleted blog persistence functions and related query parameters.
- Removed blog schemas and models from the codebase.
- Introduced common crate for shared types, including DateTimeWithTimeZoneWrapper.
- Added Thought and Follow models with corresponding migrations.
- Updated dependencies in Cargo.toml files to reflect changes.
- Adjusted tests to remove references to the blog module.

thoughts-backend/migration/src/m20250905_000001_init.rs

@@ -0,0 +1,95 @@
+use super::m20240101_000001_init::User;
+use sea_orm_migration::{prelude::*, schema::*};
+
+#[derive(DeriveMigrationName)]
+pub struct Migration;
+
+#[async_trait::async_trait]
+impl MigrationTrait for Migration {
+    async fn up(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        // --- Create Thought Table ---
+        manager
+            .create_table(
+                Table::create()
+                    .table(Thought::Table)
+                    .if_not_exists()
+                    .col(pk_auto(Thought::Id))
+                    .col(integer(Thought::AuthorId).not_null())
+                    .foreign_key(
+                        ForeignKey::create()
+                            .name("fk_thought_author_id")
+                            .from(Thought::Table, Thought::AuthorId)
+                            .to(User::Table, User::Id)
+                            .on_update(ForeignKeyAction::NoAction)
+                            .on_delete(ForeignKeyAction::Cascade),
+                    )
+                    .col(string(Thought::Content).not_null())
+                    .col(
+                        timestamp_with_time_zone(Thought::CreatedAt)
+                            .not_null()
+                            .default(Expr::current_timestamp()),
+                    )
+                    .to_owned(),
+            )
+            .await?;
+
+        // --- Create Follow Table ---
+        manager
+            .create_table(
+                Table::create()
+                    .table(Follow::Table)
+                    .if_not_exists()
+                    .col(integer(Follow::FollowerId).not_null())
+                    .col(integer(Follow::FollowedId).not_null())
+                    // Composite Primary Key to ensure a user can only follow another once
+                    .primary_key(
+                        Index::create()
+                            .col(Follow::FollowerId)
+                            .col(Follow::FollowedId),
+                    )
+                    .foreign_key(
+                        ForeignKey::create()
+                            .name("fk_follow_follower_id")
+                            .from(Follow::Table, Follow::FollowerId)
+                            .to(User::Table, User::Id)
+                            .on_delete(ForeignKeyAction::Cascade),
+                    )
+                    .foreign_key(
+                        ForeignKey::create()
+                            .name("fk_follow_followed_id")
+                            .from(Follow::Table, Follow::FollowedId)
+                            .to(User::Table, User::Id)
+                            .on_delete(ForeignKeyAction::Cascade),
+                    )
+                    .to_owned(),
+            )
+            .await
+    }
+
+    async fn down(&self, manager: &SchemaManager) -> Result<(), DbErr> {
+        manager
+            .drop_table(Table::drop().table(Follow::Table).to_owned())
+            .await?;
+        manager
+            .drop_table(Table::drop().table(Thought::Table).to_owned())
+            .await
+    }
+}
+
+#[derive(DeriveIden)]
+enum Thought {
+    Table,
+    Id,
+    AuthorId,
+    Content,
+    CreatedAt,
+}
+
+#[derive(DeriveIden)]
+enum Follow {
+    Table,
+    // The user who is initiating the follow
+    FollowerId,
+    // The user who is being followed
+    FollowedId,
+}