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/apply.sh

@@ -0,0 +1,46 @@
+# shellcheck shell=bash
+# shellcheck disable=SC2004,SC2034,SC2154  # shared state and arrays are declared in constants.sh
+# apply.sh - The only code that changes anything: confirmations and the apply flow.
+#
+# Part of create-project.sh: sourced by it, never run on its own.
+#
+# Provides: create_all, confirm_reuse, apply_plan
+
+create_all() {
+  IS_CREATION_STARTED=1
+  if ((PROJECT[has_github])); then
+    create_repository github
+  fi
+  create_repository gitea
+  if ((PROJECT[has_github])); then
+    configure_mirror
+  fi
+}
+
+confirm_reuse() {
+  local host
+  for host in github gitea; do
+    if ! is_reused "$host"; then
+      continue
+    fi
+    prompt_yes_no "The $(host_label "$host") repository $(repo_url "$host") already exists and has no real content. Reuse it" n
+    if ! ((REPLY)); then
+      die "stopped: choose another name or remove the existing repository"
+    fi
+  done
+  if ((${STATE[reuse_gitea]:-0})) && ((PROJECT[has_github])) &&
+    [[ ${STATE[gitea_repo]} == empty ]]; then
+    warn "the empty Gitea repository is reused as it is: the $AGPL_LICENSE_KEY license is not added to it"
+  fi
+}
+
+# apply_plan: the only place that changes anything on GitHub or Gitea.
+apply_plan() {
+  prompt_yes_no "Create these now" n
+  if ! ((REPLY)); then
+    say "Nothing was created."
+    return 0
+  fi
+  confirm_reuse
+  create_all
+}