fix(security): close critical auth/SSRF/RBAC holes

Verified locally end-to-end (before: exploitable, after: blocked).

- config: refuse to start on weak/default/short SECRET_KEY (was
  trivially forgeable JWT -> full admin)
- deps: add reusable require_admin dependency (JWT or API key)
- api-keys: require admin to mint/list/revoke; mask key on list
  (was unauthenticated -> instant admin API key)
- webhooks: whole router now admin-only (was fully unauthenticated
  CRUD + readable logs)
- webhook delivery: validate URL scheme + reject hosts resolving to
  private/loopback/link-local/reserved IPs; disable redirects
  (was a readable SSRF primitive)
- rbac: implement a real project-role hierarchy in check_project_role
  (was a no-op: any member, even guest, passed admin/mgr gates)
- misc: auth on delete_milestone (+ensure_can_edit_milestone),
  worklog create/delete (force caller user_id, owner-only delete),
  /activity and /export/tasks (were unauthenticated data exposure)
- tasks: auth + ensure_can_edit_task on assign_task and batch_assign

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/services/webhook.py

@@ -2,12 +2,41 @@ import json
 import hmac
 import hashlib
 import logging
+import socket
+import ipaddress
+from urllib.parse import urlparse
 from sqlalchemy.orm import Session
 from app.models.webhook import Webhook, WebhookLog
 
 logger = logging.getLogger(__name__)
 
 
+def _validate_webhook_url(url: str) -> None:
+    """Raise ValueError if the URL would target a non-public address (SSRF guard)."""
+    parsed = urlparse(url)
+    if parsed.scheme not in ("http", "https"):
+        raise ValueError(f"unsupported scheme: {parsed.scheme!r}")
+    host = parsed.hostname
+    if not host:
+        raise ValueError("missing host")
+    # Resolve every address the host maps to and reject non-global ranges.
+    try:
+        infos = socket.getaddrinfo(host, parsed.port or (443 if parsed.scheme == "https" else 80))
+    except socket.gaierror as e:
+        raise ValueError(f"DNS resolution failed: {e}")
+    for info in infos:
+        ip = ipaddress.ip_address(info[4][0])
+        if (
+            ip.is_private
+            or ip.is_loopback
+            or ip.is_link_local
+            or ip.is_multicast
+            or ip.is_reserved
+            or ip.is_unspecified
+        ):
+            raise ValueError(f"host resolves to non-public address {ip}")
+
+
 def fire_webhooks_sync(event: str, payload: dict, project_id: int, db: Session):
     """Find matching webhooks and send payloads (sync version)."""
     import httpx
@@ -35,6 +64,8 @@ def fire_webhooks_sync(event: str, payload: dict, project_id: int, db: Session):
             payload=payload_json,
         )
         try:
+            _validate_webhook_url(wh.url)
+
             headers = {"Content-Type": "application/json"}
             if wh.secret:
                 sig = hmac.new(
@@ -42,7 +73,7 @@ def fire_webhooks_sync(event: str, payload: dict, project_id: int, db: Session):
                 ).hexdigest()
                 headers["X-Webhook-Signature"] = sig
 
-            with httpx.Client(timeout=10.0) as client:
+            with httpx.Client(timeout=10.0, follow_redirects=False) as client:
                 resp = client.post(wh.url, content=payload_json, headers=headers)
                 log.response_status = resp.status_code
                 log.response_body = resp.text[:1000]