Fix BASE_URL config loading, add tasks/projects; robust .env path resolution

- Config: try ENV_FILE, .env, ../.env for loading; trim trailing slash from BaseURL
- Log BASE_URL at server startup for verification
- .env.example: document BASE_URL
- Tasks, projects, tags, migrations and related API/handlers

Made-with: Cursor

sqlc/queries/task_dependencies.sql

@@ -0,0 +1,25 @@
+-- name: AddTaskDependency :exec
+INSERT INTO task_dependencies (task_id, blocks_task_id)
+VALUES ($1, $2)
+ON CONFLICT (task_id, blocks_task_id) DO NOTHING;
+
+-- name: RemoveTaskDependency :exec
+DELETE FROM task_dependencies
+WHERE task_id = $1 AND blocks_task_id = $2;
+
+-- name: ListTaskBlockers :many
+SELECT t.* FROM tasks t
+JOIN task_dependencies td ON td.blocks_task_id = t.id
+WHERE td.task_id = $1 AND t.deleted_at IS NULL;
+
+-- name: ListTasksBlockedBy :many
+SELECT t.* FROM tasks t
+JOIN task_dependencies td ON td.task_id = t.id
+WHERE td.blocks_task_id = $1 AND t.deleted_at IS NULL;
+
+-- name: CheckDirectCircularDependency :one
+-- Direct cycle: blocks_task_id is blocked by task_id (would create A->B and B->A)
+SELECT EXISTS(
+  SELECT 1 FROM task_dependencies
+  WHERE task_id = $2 AND blocks_task_id = $1
+) AS has_circle;