feat(dispatch): implement dispatch-workflow.sh with dispatch, poll, and timeout (#4)

Add dispatch-workflow.sh script that dispatches a Gitea workflow
in another repository and polls synchronously for completion.
Refactor mock-api.sh to use Python3 HTTP server with sequence
support, enabling stateful poll-response simulation in tests.

---------

Co-authored-by: moilanik <niko.moilanen@tietoevry.com>
Reviewed-on: #4

tests/helpers/mock-server.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+import http.server, json, sys, os, threading
+
+PORT = int(sys.argv[1])
+CONFIG = sys.argv[2]
+REQ_FILE = sys.argv[3]
+
+idx_lock = threading.Lock()
+mode = 'SINGLE'
+default_code = 200
+responses = []
+idx_path = ''
+
+with open(CONFIG) as f:
+    mode = f.readline().strip()
+    if mode == 'SEQUENCE':
+        seq_raw = f.readline().strip()
+        idx_path = f.readline().strip()
+        responses = json.loads(seq_raw)
+    else:
+        default_code = int(f.readline().strip())
+
+def read_idx():
+    try:
+        with open(idx_path) as f2:
+            return int(f2.read().strip())
+    except:
+        return 0
+
+def write_idx(v):
+    with open(idx_path, 'w') as f2:
+        f2.write(str(v))
+
+class H(http.server.BaseHTTPRequestHandler):
+    def _get_response(self):
+        if mode == 'SEQUENCE':
+            with idx_lock:
+                i = read_idx()
+                r = responses[min(i, len(responses)-1)]
+                write_idx(i + 1)
+            code = r.get('code', 200)
+            body = r.get('body', {'id':1})
+            return code, json.dumps(body)
+        return default_code, json.dumps({'id':1})
+
+    def _log_request(self, method):
+        path = self.path
+        content_len = int(self.headers.get('Content-Length', 0))
+        body = self.rfile.read(content_len).decode() if content_len else ''
+        line = f'{method} {path}\n{body}\n'
+        with open(REQ_FILE, 'a') as f:
+            f.write(line)
+
+    def do_GET(self):
+        self._log_request('GET')
+        code, body = self._get_response()
+        self.send_response(code)
+        self.send_header('Content-Type', 'application/json')
+        self.end_headers()
+        self.wfile.write(body.encode())
+
+    def do_POST(self):
+        self._log_request('POST')
+        code, body = self._get_response()
+        self.send_response(code)
+        self.send_header('Content-Type', 'application/json')
+        self.end_headers()
+        self.wfile.write(body.encode())
+
+    def log_message(self, format, *args):
+        pass
+
+s = http.server.HTTPServer(('', PORT), H)
+s.allow_reuse_address = True
+s.serve_forever()