tightened network defaults, squashed bugs

Security:
- Bind HTTP gateway to 127.0.0.1 by default; add --bind for LAN opt-in
- Restrict Reticulum mesh surface to GET /api/sites only (CSRF cannot
  authenticate mesh callers, so gate by whitelist)
- Cap request body size at 16 MiB to prevent memory DoS
- Redact /bookmark query strings from request logs so the bookmark token
  and URLs do not land in stdout / docker / journal logs
- Tighten FTS5 sanitizer: strip colon, drop AND/OR/NOT/NEAR operator words
- Expand .dockerignore; document trust model in README

Features:
- Add sharing mode toggle (share everything except private vs share only
  public-tagged) with /share/preview so users can see what subscribers
  would receive before enabling sharing

Bugs:
- handle_export() crashed on every call (missing query kwarg)
- Dead float16 decompression branch in embeddings.py silently corrupted
  the HNSW index when compress_embeddings was on
- GATEWAY_PORT staleness: --port and find_available_port had no effect
  on the actual bind
- semantic_search default mismatched between db.py ("1") and the rest of
  the app ("0"), causing embeddings to be generated when the UI said off
- Connection pool returned connections with uncommitted transactions to
  the next consumer
- Gateway POST body decode 502'd on non-UTF-8 input
- ensure_rns_config clobbered user-edited ~/.reticulum/config; now only
  rewrites files it authored (sentinel-tagged)

app.py

@@ -8,7 +8,8 @@ from http.server import HTTPServer
 
 from db import init_db, get_setting, set_setting
 from handlers import dispatch_request
-from gateway import GatewayState, GatewayHandler, GATEWAY_PORT
+import gateway
+from gateway import GatewayState, GatewayHandler
 
 APP_NAME = "tinyweb"
 ASPECTS = ["server"]
@@ -24,13 +25,13 @@ def get_transport_config():
     return host, int(port)
 
 
-def find_available_port(start=8080, max_attempts=20):
+def find_available_port(start=8080, max_attempts=20, host="127.0.0.1"):
     """Find an available port starting from start."""
     import socket
     for port in range(start, start + max_attempts):
         try:
             with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
-                s.bind(("0.0.0.0", port))
+                s.bind((host, port))
             return port
         except OSError:
             continue
@@ -71,16 +72,32 @@ def load_or_create_identity():
     return identity
 
 
+# Remote peers on the Reticulum mesh can only reach a narrow, read-only surface.
+# Any other method/path is rejected here — CSRF cannot authenticate mesh callers
+# (the attacker controls both the "cookie" and the "form" side of the check), so
+# gating by whitelist is the only safe option.
+_RNS_ALLOWED = {("GET", "/api/sites")}
+
+
 def rns_request_handler(path, data, request_id, link_id, remote_identity, requested_at):
     if data is None:
         data = {"method": "GET", "path": "/", "query": {}, "body": {}, "gateway_host": ""}
+    method = data.get("method", "GET")
+    req_path = data.get("path", "/")
+    if (method, req_path) not in _RNS_ALLOWED:
+        return {
+            "status": 403,
+            "content_type": "text/plain; charset=utf-8",
+            "body": "Forbidden: this endpoint is not available over Reticulum.",
+            "headers": {},
+        }
     return dispatch_request(data)
 
 
-def start_gateway(reticulum):
+def start_gateway(reticulum, bind_host="127.0.0.1"):
     GatewayState.reticulum = reticulum
     GatewayState.local_dispatch = dispatch_request
-    server = HTTPServer(("0.0.0.0", GATEWAY_PORT), GatewayHandler)
+    server = HTTPServer((bind_host, gateway.GATEWAY_PORT), GatewayHandler)
     thread = threading.Thread(target=server.serve_forever, daemon=True)
     thread.start()
 
@@ -126,7 +143,21 @@ def ensure_rns_config(config_dir, transport_host=None, transport_port=None):
     if transport_port is None:
         transport_port = int(get_setting("transport_port", str(DEFAULT_TRANSPORT_PORT)))
 
+    managed_sentinel = "# managed by tinyweb"
     if os.path.exists(config_file):
+        try:
+            with open(config_file) as f:
+                existing = f.read()
+        except OSError:
+            existing = ""
+        if managed_sentinel not in existing:
+            # User-authored config — don't clobber it.
+            if not _config_settings_match(config_file, transport_host, transport_port):
+                print(
+                    f"Warning: {config_file} was not created by tinyweb; "
+                    "leaving it alone. Edit it manually to change transport/LoRa settings."
+                )
+            return
         if _config_settings_match(config_file, transport_host, transport_port):
             return
 
@@ -164,7 +195,8 @@ def ensure_rns_config(config_dir, transport_host=None, transport_port=None):
 
     os.makedirs(config_dir, exist_ok=True)
     with open(config_file, "w") as f:
-        f.write(f"""[reticulum]
+        f.write(f"""{managed_sentinel}
+[reticulum]
   enable_transport = False
   share_instance = No
 
@@ -201,15 +233,20 @@ def main():
     parser = argparse.ArgumentParser(prog="tinyweb", description="Personal decentralized search engine")
     parser.add_argument("--version", "-v", action="store_true", help="Show version")
     parser.add_argument("--port", "-p", type=int, default=None, help="HTTP gateway port (default: 8080)")
+    parser.add_argument(
+        "--bind", "-b", default="127.0.0.1",
+        help="Address to bind the HTTP gateway to (default: 127.0.0.1). "
+             "Use 0.0.0.0 to expose to the LAN; note that the web UI has no authentication.",
+    )
     args = parser.parse_args()
 
     if args.version:
         print(f"TinyWeb {get_version()}")
         return
 
+    bind_host = args.bind
     port = args.port or 8080
-    import gateway
-    gateway.GATEWAY_PORT = find_available_port(port)
+    gateway.GATEWAY_PORT = find_available_port(port, host=bind_host)
 
     init_db()
     transport_host = get_setting("transport_host", DEFAULT_TRANSPORT_HOST)
@@ -238,10 +275,15 @@ def main():
     time.sleep(2)
     destination.announce()
     set_setting("dest_hash", destination.hash.hex())
-    start_gateway(reticulum)
+    start_gateway(reticulum, bind_host=bind_host)
 
     print(f"TinyWeb running!")
-    print(f"Open http://localhost:{GATEWAY_PORT} in your browser")
+    if bind_host in ("0.0.0.0", "::"):
+        print(f"Open http://localhost:{gateway.GATEWAY_PORT} in your browser")
+        print(f"WARNING: listening on {bind_host} — the web UI has no authentication. "
+              "Anyone on your network can control this instance.")
+    else:
+        print(f"Open http://{bind_host}:{gateway.GATEWAY_PORT} in your browser")
     print(f"Destination hash: {RNS.prettyhexrep(destination.hash)} (share this so friends can subscribe)")
 
     while True: