Create Initial Database Schema for Tasks. (#1)

Create migration scripts for this and initial Task DB Model in rust along with unit tests.

Reviewed-on: #1
Co-authored-by: Drew Galbraith <drew@tiramisu.one>
Co-committed-by: Drew Galbraith <drew@tiramisu.one>

backend/migrations/20250823023643_create_tasks.down.sql

@@ -0,0 +1,2 @@
+-- Add down migration script here
+DROP TABLE tasks

backend/migrations/20250823023643_create_tasks.up.sql

@@ -0,0 +1,10 @@
+-- Add up migration script here
+CREATE TABLE tasks (
+    id UUID PRIMARY KEY NOT NULL,
+    title VARCHAR NOT NULL,
+    description TEXT,
+    status TEXT CHECK(status IN ('todo', 'done', 'backlog')) DEFAULT 'todo',
+    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    completed_at TIMESTAMP
+);