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>

apps/timesfm-forecast/examples/sample.csv

@@ -0,0 +1,33 @@
+
+date,value,key
+2022-01-01,120,A
+2022-02-01,118,A
+2022-03-01,121,A
+2022-04-01,123,A
+2022-05-01,125,A
+2022-06-01,127,A
+2022-07-01,130,A
+2022-08-01,129,A
+2022-09-01,131,A
+2022-10-01,133,A
+2022-11-01,135,A
+2022-12-01,138,A
+2023-01-01,140,A
+2023-02-01,142,A
+2023-03-01,145,A
+
+2022-01-01,80,B
+2022-02-01,82,B
+2022-03-01,81,B
+2022-04-01,83,B
+2022-05-01,84,B
+2022-06-01,85,B
+2022-07-01,87,B
+2022-08-01,88,B
+2022-09-01,90,B
+2022-10-01,89,B
+2022-11-01,91,B
+2022-12-01,92,B
+2023-01-01,93,B
+2023-02-01,95,B
+2023-03-01,96,B