refactor: restructure monorepo for clean portfolio layout

- Move timesfm-forecast into apps/ directory
- Flatten Udacity portfolio projects from deep URL-encoded paths
  into data-engineering/01-XX numbered directories
- Remove old My-Data-Engineering-Portifolio/ parent directory
- Rewrite root README.md: professional overview with badges,
  project table, and repo structure diagram
- Create data-engineering/README.md with per-project descriptions
- Add README.md for 02-cassandra-modeling (was missing)
- Add README.md for 05-airflow-pipelines (was missing)
- Normalize capstone readme.md -> README.md
- Update .gitignore: add *.cfg, *.env, *.zip, *.sas7bdat,
  Jupyter checkpoints, IDE dirs; remove uv.lock exclusion
- Add dwh.cfg.example and dl.cfg.example credential templates
- Untrack real credential files (dwh.cfg, dl.cfg)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

data-engineering/05-airflow-pipelines/create_tables.sql

@@ -0,0 +1,83 @@
+CREATE TABLE public.artists (
+	artistid varchar(256) NOT NULL,
+	name varchar(256),
+	location varchar(256),
+	lattitude numeric(18,0),
+	longitude numeric(18,0)
+);
+
+CREATE TABLE public.songplays (
+	playid varchar(32) NOT NULL,
+	start_time timestamp NOT NULL,
+	userid int4 NOT NULL,
+	"level" varchar(256),
+	songid varchar(256),
+	artistid varchar(256),
+	sessionid int4,
+	location varchar(256),
+	user_agent varchar(256),
+	CONSTRAINT songplays_pkey PRIMARY KEY (playid)
+);
+
+CREATE TABLE public.songs (
+	songid varchar(256) NOT NULL,
+	title varchar(256),
+	artistid varchar(256),
+	"year" int4,
+	duration numeric(18,0),
+	CONSTRAINT songs_pkey PRIMARY KEY (songid)
+);
+
+CREATE TABLE public.staging_events (
+	artist varchar(256),
+	auth varchar(256),
+	firstname varchar(256),
+	gender varchar(256),
+	iteminsession int4,
+	lastname varchar(256),
+	length numeric(18,0),
+	"level" varchar(256),
+	location varchar(256),
+	"method" varchar(256),
+	page varchar(256),
+	registration numeric(18,0),
+	sessionid int4,
+	song varchar(256),
+	status int4,
+	ts int8,
+	useragent varchar(256),
+	userid int4
+);
+
+CREATE TABLE public.staging_songs (
+	num_songs int4,
+	artist_id varchar(256),
+	artist_name varchar(256),
+	artist_latitude numeric(18,0),
+	artist_longitude numeric(18,0),
+	artist_location varchar(256),
+	song_id varchar(256),
+	title varchar(256),
+	duration numeric(18,0),
+	"year" int4
+);
+
+CREATE TABLE public."time" (
+	start_time timestamp NOT NULL,
+	"hour" int4,
+	"day" int4,
+	week int4,
+	"month" varchar(256),
+	"year" int4,
+	weekday varchar(256),
+	CONSTRAINT time_pkey PRIMARY KEY (start_time)
+) ;
+
+CREATE TABLE public.users (
+	userid int4 NOT NULL,
+	first_name varchar(256),
+	last_name varchar(256),
+	gender varchar(256),
+	"level" varchar(256),
+	CONSTRAINT users_pkey PRIMARY KEY (userid)
+);