feat(ui): 11-point UI overhaul — tabs, transfers, settings, uploads

Hub/UI:
- Icon-only group tabs (chat, files, settings) with per-group default tab
- Transfer widget: filename becomes a clickable link to open completed downloads
- Pulse animation on transfer icon (pale→dark green) while active
- Download button feedback in FilePreview (spinner, auto-reset)
- Group mute toggle persists across navigation
- Login page autofocus, chat refocus after send
- Theme toggle closes menu, status badge and duplicate connecting removed
- Create-folder restricted to operators, download-path note removed
- User preferences API (CRUD) with Alembic migration
- Profile: email display/edit via PATCH /v1/users/me
- Settings: "Defaults" section for default tab selector
- All 10 locale files updated

Node:
- upload_dir in node.toml: separate filesystem path for uploads
- Root.direct flag: uploads land at root path, no subdirectory
- CLI --upload-dir flag on `group add`
- Admin UI accepts upload_dir

Client (Electron):
- shell.openPath bridge for opening completed downloads
- platform.js passes open callback from native save

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

2 files changed, 39 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/db/migrations/versions/f1a2b3c4d5e6_add_user_preferences.py b/packages/meshbay-hub/src/meshbay_hub/db/migrations/versions/f1a2b3c4d5e6_add_user_preferences.py
new file mode 100644
index 0000000..e30a4da
--- /dev/null
+++ b/packages/meshbay-hub/src/meshbay_hub/db/migrations/versions/f1a2b3c4d5e6_add_user_preferences.py
@@ -0,0 +1,30 @@
+"""add_user_preferences
+
+Revision ID: f1a2b3c4d5e6
+Revises: d28b9caf9f07
+Create Date: 2026-08-19 12:00:00.000000
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision: str = 'f1a2b3c4d5e6'
+down_revision: Union[str, Sequence[str], None] = 'd28b9caf9f07'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table('user_preferences',
+        sa.Column('user_id', sa.String(36), sa.ForeignKey('users.id'), nullable=False),
+        sa.Column('key', sa.String(64), nullable=False),
+        sa.Column('value', sa.Text(), nullable=False),
+        sa.PrimaryKeyConstraint('user_id', 'key'),
+    )
+
+
+def downgrade() -> None:
+    op.drop_table('user_preferences')
diff --git a/packages/meshbay-hub/src/meshbay_hub/db/models.py b/packages/meshbay-hub/src/meshbay_hub/db/models.py
index 12507a6..f1f11e2 100644
--- a/packages/meshbay-hub/src/meshbay_hub/db/models.py
+++ b/packages/meshbay-hub/src/meshbay_hub/db/models.py
@@ -288,6 +288,15 @@ class ContentBlocklist(Base):
     added_by:     Mapped[str | None] = mapped_column(String(64))  # "auto" or admin username
 
 
+class UserPreference(Base):
+    __tablename__ = "user_preferences"
+
+    user_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("users.id"), primary_key=True)
+    key:     Mapped[str] = mapped_column(String(64), primary_key=True)
+    value:   Mapped[str] = mapped_column(Text, nullable=False)
+
+
 class IPLog(Base):
     """
     Connection log for legal compliance.