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/api.sh

@@ -0,0 +1,61 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2004,SC2034,SC2154  # shared state and arrays are declared in constants.sh
+# api.sh - Calls to the GitHub and Gitea APIs and the reporting of a refused call.
+#
+# Part of create-project.sh: sourced by it, never run on its own.
+#
+# Provides: host_label, api_call, server_message, fail_request, expect_status
+
+host_label() {
+  case "$1" in
+    gitea) printf 'Gitea' ;;
+    github) printf 'GitHub' ;;
+    *) die "internal error: unknown host" ;;
+  esac
+}
+
+# api_call HOST METHOD PATH [BODY]: HOST is gitea or github. A network
+# failure ends the run; the HTTP status is left in HTTP_STATUS.
+api_call() {
+  local host="$1" method="$2" path="$3" body="${4:-}"
+  case "$host" in
+    gitea)
+      http_request "$method" "${CONFIG[GITEA_API_URL]}$path" token \
+        "${CREDENTIALS[GITEA_TOKEN]}" "$body" || die "$HTTP_ERROR"
+      ;;
+    github)
+      http_request "$method" "${CONFIG[GITHUB_API_URL]}$path" bearer \
+        "${CREDENTIALS[GITHUB_PAT]}" "$body" || die "$HTTP_ERROR"
+      ;;
+    *) die "internal error: unknown host" ;;
+  esac
+}
+
+# server_message: the "message" of the last response, cleaned and shortened.
+server_message() {
+  local message
+  # A response that is not JSON must not stop the error report.
+  message="$(json_get "$HTTP_BODY_FILE" message 2>/dev/null || true)"
+  message="${message//[[:cntrl:]]/ }"
+  printf '%s' "${message:0:160}"
+}
+
+fail_request() {
+  local detail message
+  detail="$(describe_http_status "$HTTP_STATUS")"
+  message="$(server_message)"
+  die "$1: $detail${message:+ (the server says: $message)}"
+}
+
+# expect_status CONTEXT CODE...: go on if the last status is one of CODE,
+# otherwise stop with CONTEXT and the server's own words.
+expect_status() {
+  local context="$1" code
+  shift
+  for code in "$@"; do
+    if [[ $HTTP_STATUS == "$code" ]]; then
+      return 0
+    fi
+  done
+  fail_request "$context"
+}