Add the GitHub and Gitea steps and split the script into library files

Dry run by default: the script reads from both hosts (tokens, owners,
names, license, SSH) and prints a plan; --apply creates the repositories
and the Gitea -> GitHub push mirror after a final yes. Choosing GitHub
applies the AGPL-3.0 license to the Gitea repository. A failed step is
reported with what exists and how to continue; nothing is ever deleted.

create-project.sh is now the entry point; the work lives in src/lib/, one
responsibility per file. .gitignore gets !src/lib (the Python template
ignores any lib/ folder). Tests grow to 599 checks, with a stub curl and
ssh, and guards for the file structure.

Task: MIL-002#1
Task: MIL-002#2
Task: MIL-002#3
Task: MIL-002#4
Task: MIL-002#5
Task: MIL-002#6
Refs #9
Refs #10
Refs #11
Refs #12
Refs #13
Refs #14

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/lib/temp.sh

@@ -0,0 +1,31 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2004,SC2034,SC2154  # shared state and arrays are declared in constants.sh
+# temp.sh - Private temporary files and their cleanup (never a recursive delete).
+#
+# Part of create-project.sh: sourced by it, never run on its own.
+#
+# Provides: cleanup, setup_temp_dir, make_temp_file
+
+# Files are removed one by one and the directory with rmdir: a recursive
+# delete is never needed and never used.
+cleanup() {
+  local file
+  for file in "${TEMP_FILES[@]}"; do
+    rm -f -- "$file"
+  done
+  if [[ -n $TMP_DIR && -d $TMP_DIR ]]; then
+    # rmdir fails only if something unexpected is left inside; leave it
+    # rather than delete files this script did not create.
+    rmdir -- "$TMP_DIR" 2>/dev/null || true
+  fi
+}
+
+setup_temp_dir() {
+  TMP_DIR="$(umask 077 && mktemp -d "${TMPDIR:-/tmp}/repofoundry.XXXXXX")"
+}
+
+# make_temp_file: create a private file in TMP_DIR and return it in REPLY.
+make_temp_file() {
+  REPLY="$(umask 077 && mktemp "$TMP_DIR/file.XXXXXX")"
+  TEMP_FILES+=("$REPLY")
+}