Add v1 shortener: Bearer API, public 302, landing, and CI.

Standalone Django service so callers can mint links and phones get a 302.
Closes #1.

site/links/views.py

@@ -0,0 +1,31 @@
+"""Public redirect — no auth. SMS recipients tap GET /<code>."""
+
+from __future__ import annotations
+
+import re
+
+from django.http import Http404, HttpResponseRedirect
+from django.views.decorators.http import require_http_methods
+
+from links.models import ShortLink
+from links.services import record_click_best_effort
+
+CODE_RE = re.compile(r"^[a-z0-9]{4,8}$")
+
+
+@require_http_methods(["GET", "HEAD"])
+def redirect_view(request, code: str):
+    if not CODE_RE.fullmatch(code):
+        raise Http404()
+
+    try:
+        link = ShortLink.objects.get(code=code)
+    except ShortLink.DoesNotExist as exc:
+        raise Http404() from exc
+
+    if not link.is_available():
+        raise Http404()
+
+    if request.method == "GET":
+        record_click_best_effort(request, link)
+    return HttpResponseRedirect(link.target_url)