Initial dictionary producer: builddict, word-list sources, DAWG build + CI

- builddict drives the de-internalized scrabble-solver dictdawg/wordlist builders
  (pinned v1.0.0) to produce the three DAWGs (en_sowpods, ru_scrabble, ru_erudit),
  byte-identical to the solver's committed fixtures (same dafsa/alphabet v1.1.0 -> no
  index drift with the running backend).
- Sources: english/sowpods.txt vendored from kamilmielnik/scrabble-dictionaries;
  russian/scrabble.txt + the dictprep tooling moved out of scrabble-solver.
- CI builds the DAWGs on push/PR and, on a vX.Y.Z tag, packages them flat into
  scrabble-dawg-<tag>.tar.gz and attaches it to the Gitea release.

Makefile

@@ -0,0 +1,34 @@
+# scrabble-dictionary build helpers.
+#
+# `make dawg` (re)builds the dictionary DAWGs under dawg/ from their word lists, using the
+# published scrabble-solver dictdawg/wordlist builders (pinned in go.mod), so the on-disk
+# format and letter indexing match the running backend exactly (no index drift):
+#   en_sowpods.dawg  — English SOWPODS (Latin alphabet)
+#   ru_scrabble.dawg — Russian Scrabble nouns (Cyrillic, 33 letters)
+#   ru_erudit.dawg   — Эрудит (the same list with Ё→Е folded and de-duped)
+#
+# The CI workflow packages dawg/*.dawg into a release artifact on a vX.Y.Z tag.
+
+export GOPRIVATE := gitea.iliadenisov.ru/*
+
+GO        ?= go
+PYTHON    ?= python3
+DAWG_DIR  := dawg
+BUILDDICT := $(GO) run ./cmd/builddict
+
+.PHONY: dawg dawg-en dawg-ru dawg-erudit clean-dawg
+
+dawg: dawg-en dawg-ru dawg-erudit
+
+dawg-en:
+	$(BUILDDICT) -dict dictionaries/english/sowpods.txt -alphabet latin -name en_sowpods -out $(DAWG_DIR)
+
+dawg-ru:
+	$(BUILDDICT) -dict dictprep/russian/scrabble.txt -alphabet russian -name ru_scrabble -out $(DAWG_DIR)
+
+dawg-erudit:
+	$(PYTHON) dictprep/fold_yo.py dictprep/russian/scrabble.txt > /tmp/ru_erudit_words.txt
+	$(BUILDDICT) -dict /tmp/ru_erudit_words.txt -alphabet russian -name ru_erudit -out $(DAWG_DIR)
+
+clean-dawg:
+	rm -f $(DAWG_DIR)/*.dawg