feat: password-based key derivation + operational QUICKSTART

keyderive.py: derive Ed25519+X25519 from username+password via Argon2id.
Same credentials → same keys on any device. Encrypt/decrypt keypair
bundle (AES-256-GCM) for hub storage (web clients).
7/7 tests. Full suite: 81/81.

keyderive.js: browser counterpart using PBKDF2-SHA512 + random keypairs
encrypted for hub storage. Avoids algorithm mismatch with Python.

hub/models.py + users.py: keypair_bundle field added to User, stored on
registration, returned in login response for web client key recovery.

QUICKSTART.md: fully rewritten. 3 operational scripts in QE/demo-v1/:
  setup_demo.py  — create accounts, group, distribute GEK
  run_node.py    — start HTTP node (watches shared/ directory)
  download.py    — bob login → GEK fetch → decrypt → save
All tested locally end-to-end. No invented URLs.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/api/users.py b/packages/meshbay-hub/src/meshbay_hub/api/users.py
index 0b615a4..5a7a3b4 100644
--- a/packages/meshbay-hub/src/meshbay_hub/api/users.py
+++ b/packages/meshbay-hub/src/meshbay_hub/api/users.py
@@ -42,8 +42,9 @@ class RegisterRequest(BaseModel):
     username:        str
     email:           str
     password:        str
-    pk_user_ed25519: str   # base64 raw 32B
-    pk_user_x25519:  str   # base64 raw 32B
+    pk_user_ed25519: str        # base64 raw 32B
+    pk_user_x25519:  str        # base64 raw 32B
+    keypair_bundle:  str | None = None  # AES-GCM encrypted bundle (web clients)
 
     @field_validator("username")
     @classmethod
@@ -95,6 +96,7 @@ async def register(
         pk_ed25519=body.pk_user_ed25519,
         pk_x25519=body.pk_user_x25519,
         hub_id=hub_id,
+        keypair_bundle=body.keypair_bundle,
     )
     db.add(user)
     db.add(IPLog(
@@ -142,12 +144,15 @@ async def login(
     db.add(IPLog(user_id=user.id, event="login", ip_address=ip))
     await db.commit()
 
-    return {
+    resp = {
         "access_token":  access_token,
         "refresh_token": raw_rt,
         "token_type":    "bearer",
         "expires_in":    _ttl(),
     }
+    if user.keypair_bundle:
+        resp["keypair_bundle"] = user.keypair_bundle   # encrypted, for web clients
+    return resp
 
 
 @router.post("/token/refresh")