Add Phase 4: code quality, CI/CD, and formatting

- testthat infrastructure with 15 tests covering env-var guards,
  return types for all format/save functions, and spelling
- inst/WORDLIST with 52 domain terms (LightGBM, MinIO, Parquet, etc.)
- Spelling test wired into devtools::test() via test-spelling.R
- styler::style_file() added as step 0 in deploy.R (auto-fixes before ship)
- .gitea/workflows/test.yaml: runs testthat suite on push
- .gitea/workflows/lint.yaml: lychee link check + styler dry-run on push
- Removed internal IP address from comment in train_production_model()
- Language: en-US added to DESCRIPTION

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

DESCRIPTION

@@ -10,6 +10,7 @@ Description: Tools to ingest the Bank Account Fraud (BAF) Base dataset into a
     targets.
 License: MIT + file LICENSE
 Encoding: UTF-8
+Language: en-US
 Roxygen: list(markdown = TRUE)
 RoxygenNote: 7.3.3
 Imports:
@@ -29,6 +30,11 @@ Suggests:
     targets,
     tarchetypes,
     knitr,
-    scales
+    scales,
+    spelling,
+    testthat (>= 3.0.0),
+    withr,
+    ggplot2
+Config/testthat/edition: 3
 URL: https://docs.robwiederstein.org/baflakehouse
 BugReports: https://git.robwiederstein.org/rkw/bank-fraud-baf-lakehouse/issues