fix: Chat search index, DMS group-share user_id, verify workflows and mail salt

- Implement CommSearchProvider: index_message(), reindex_all() with FTS + vector search
- Add migration 0035: search_tsv + embedding columns on comm_messages
- Fix DMS group-share: use current_user user_id instead of random uuid4()
- Workflows already DB-configurable (seed from onboarding.py, loaded from DB)
- Mail salt already dynamic with legacy fallback (migration 0026)

alembic/versions/0035_comm_search_index.py

@@ -0,0 +1,51 @@
+"""Add search_tsv and embedding columns to comm_messages for full-text search indexing.
+
+Revision ID: 0035
+Revises: 0034_automation_config
+Create Date: 2026-07-25
+"""
+
+from __future__ import annotations
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import TSVECTOR
+
+revision: str = "0035_comm_search_index"
+down_revision: Union[str, None] = "0034_automation_config"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Add search_tsv column for full-text search
+    op.add_column(
+        "comm_messages",
+        sa.Column("search_tsv", TSVECTOR, nullable=True),
+    )
+    # Add embedding column for vector search (768 dimensions matching pgvector)
+    op.execute(
+        "ALTER TABLE comm_messages ADD COLUMN embedding vector(768)"
+    )
+    # Create GIN index on search_tsv for fast FTS queries
+    op.create_index(
+        "ix_comm_messages_search_tsv",
+        "comm_messages",
+        ["search_tsv"],
+        postgresql_using="gin",
+    )
+    # Create IVFFlat index on embedding for fast vector search
+    op.execute(
+        "CREATE INDEX IF NOT EXISTS ix_comm_messages_embedding "
+        "ON comm_messages USING ivfflat (embedding vector_cosine_ops) "
+        "WITH (lists = 100)"
+    )
+
+
+def downgrade() -> None:
+    op.drop_index("ix_comm_messages_embedding", table_name="comm_messages")
+    op.drop_index("ix_comm_messages_search_tsv", table_name="comm_messages")
+    op.drop_column("comm_messages", "embedding")
+    op.drop_column("comm_messages", "search_tsv")