Create a plan for implementing projects and also create the backend API. (#19)

Creates projects to organize tasks under. (Note the migration also contains the tables for creating folders for projects as well because adding foreign keys is a PITA in sqlite apparently).

Reviewed-on: #19
Co-authored-by: Drew Galbraith <drew@tiramisu.one>
Co-committed-by: Drew Galbraith <drew@tiramisu.one>

backend/migrations/20251023043152_create_projects.down.sql

@@ -0,0 +1,17 @@
+ALTER TABLE tasks  RENAME TO tasks_old;
+
+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
+);
+
+INSERT INTO tasks SELECT id, title, description, status, created_at, updated_at, completed_at FROM tasks_old;
+
+DROP TABLE tasks_old;
+DROP TABLE projects;
+DROP TABLE folders;