fix(security): RBAC on legacy create endpoints, hashed API keys, hardening

Addresses findings from the security audit:
- H1: add check_project_role to the legacy misc.py create endpoints
  (milestones=mgr, tasks/supports/meetings=dev) that previously required
  only authentication — closing a cross-project write bypass available to
  any logged-in user or agent API key.
- M2: comments are always attributed to the authenticated caller; the
  client-supplied author_id is dropped (no author spoofing).
- M3: API keys are stored as SHA-256 hashes (key_hash) plus a short
  key_prefix for display — never plaintext. Lookup hashes the presented
  key; listings never expose the secret. Includes an idempotent migration
  for existing deployments.
- M5: the OIDC session cookie's Secure flag is env-driven via
  SESSION_COOKIE_SECURE (default True; set false for plain-HTTP dev).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/core/config.py

@@ -22,6 +22,10 @@ class Settings(BaseSettings):
     # in via a bound OIDC identity / API keys), frontend hides password UI.
     HARBORFORGE_OIDC_ONLY: bool = False
 
+    # Mark the OIDC state/session cookie Secure (HTTPS-only). Defaults to True
+    # for production; set SESSION_COOKIE_SECURE=false for plain-HTTP local dev.
+    SESSION_COOKIE_SECURE: bool = True
+
     class Config:
         env_file = ".env"