Add multi-user auth, background generation, and chat UX improvements

Phase 5: Multi-user authentication with session cookies, bcrypt passwords,
first-user-is-admin pattern, per-user data isolation, backup/restore,
Docker Swarm production stack with secrets and network isolation.

Phase 5.1: Chat UX improvements:
- Background generation architecture (GenerationBuffer + asyncio task)
  with SSE fan-out, reconnect support, and periodic DB flushes
- LLM-generated conversation titles (first exchange + every 10th message)
- Stop generation button with cancel_event and partial content preservation
- Relative timestamps in sidebar (5m ago, 3h ago, then dates)
- Empty chat auto-cleanup on navigation away
- Save-as-note uses LLM for title generation, tags notes with "chat"
- Summarize-as-note also tags with "chat"

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

alembic/versions/0008_add_users_and_user_id.py

@@ -0,0 +1,121 @@
+"""add users table and user_id columns
+
+Revision ID: 0008
+Revises: 0007
+Create Date: 2026-02-11 00:00:00.000000
+"""
+
+from alembic import op
+
+revision = "0008"
+down_revision = "0007"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # Create users table
+    op.execute("""
+        CREATE TABLE IF NOT EXISTS users (
+            id SERIAL PRIMARY KEY,
+            username TEXT UNIQUE NOT NULL,
+            email TEXT,
+            password_hash TEXT NOT NULL,
+            role TEXT NOT NULL DEFAULT 'user',
+            created_at TIMESTAMPTZ DEFAULT now()
+        )
+    """)
+    op.execute("CREATE INDEX IF NOT EXISTS ix_users_username ON users (username)")
+
+    # Add user_id columns WITHOUT FK constraints first (so we can assign existing rows)
+    op.execute("""
+        DO $$ BEGIN
+            ALTER TABLE notes ADD COLUMN user_id INTEGER;
+        EXCEPTION WHEN duplicate_column THEN NULL;
+        END $$
+    """)
+    op.execute("""
+        DO $$ BEGIN
+            ALTER TABLE conversations ADD COLUMN user_id INTEGER;
+        EXCEPTION WHEN duplicate_column THEN NULL;
+        END $$
+    """)
+    op.execute("""
+        DO $$ BEGIN
+            ALTER TABLE settings ADD COLUMN user_id INTEGER NOT NULL DEFAULT 1;
+        EXCEPTION WHEN duplicate_column THEN NULL;
+        END $$
+    """)
+
+    # Assign all existing data to user_id=1 (the first registered user gets SERIAL id=1)
+    op.execute("UPDATE notes SET user_id = 1 WHERE user_id IS NULL")
+    op.execute("UPDATE conversations SET user_id = 1 WHERE user_id IS NULL")
+    op.execute("UPDATE settings SET user_id = 1 WHERE user_id != 1")
+
+    # Restructure settings PK: drop old single-column PK, create composite (user_id, key)
+    op.execute("""
+        DO $$ BEGIN
+            ALTER TABLE settings DROP CONSTRAINT settings_pkey;
+        EXCEPTION WHEN undefined_object THEN NULL;
+        END $$
+    """)
+    op.execute("""
+        DO $$ BEGIN
+            ALTER TABLE settings ADD CONSTRAINT settings_pkey PRIMARY KEY (user_id, key);
+        EXCEPTION WHEN duplicate_object THEN NULL;
+        END $$
+    """)
+
+    # Now add FK constraints with NOT VALID (skips validation of existing rows
+    # where user_id=1 has no matching user yet — becomes valid once first user registers)
+    op.execute("""
+        DO $$ BEGIN
+            ALTER TABLE notes ADD CONSTRAINT notes_user_id_fkey
+                FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE NOT VALID;
+        EXCEPTION WHEN duplicate_object THEN NULL;
+        END $$
+    """)
+    op.execute("""
+        DO $$ BEGIN
+            ALTER TABLE conversations ADD CONSTRAINT conversations_user_id_fkey
+                FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE NOT VALID;
+        EXCEPTION WHEN duplicate_object THEN NULL;
+        END $$
+    """)
+    op.execute("""
+        DO $$ BEGIN
+            ALTER TABLE settings ADD CONSTRAINT settings_user_id_fkey
+                FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE NOT VALID;
+        EXCEPTION WHEN duplicate_object THEN NULL;
+        END $$
+    """)
+
+    op.execute("CREATE INDEX IF NOT EXISTS ix_notes_user_id ON notes (user_id)")
+    op.execute("CREATE INDEX IF NOT EXISTS ix_conversations_user_id ON conversations (user_id)")
+
+
+def downgrade() -> None:
+    # Reverse settings changes
+    op.execute("""
+        DO $$ BEGIN
+            ALTER TABLE settings DROP CONSTRAINT settings_pkey;
+        EXCEPTION WHEN undefined_object THEN NULL;
+        END $$
+    """)
+    op.execute("ALTER TABLE settings ALTER COLUMN user_id DROP NOT NULL")
+    op.execute("""
+        DO $$ BEGIN
+            ALTER TABLE settings ADD CONSTRAINT settings_pkey PRIMARY KEY (key);
+        EXCEPTION WHEN duplicate_object THEN NULL;
+        END $$
+    """)
+    op.execute("ALTER TABLE settings DROP COLUMN IF EXISTS user_id")
+
+    op.execute("DROP INDEX IF EXISTS ix_conversations_user_id")
+    op.execute("ALTER TABLE conversations DROP COLUMN IF EXISTS user_id")
+
+    op.execute("DROP INDEX IF EXISTS ix_notes_user_id")
+    op.execute("ALTER TABLE notes DROP COLUMN IF EXISTS user_id")
+
+    op.execute("DROP INDEX IF EXISTS ix_users_username")
+    op.execute("DROP TABLE IF EXISTS users")

alembic/versions/0009_add_message_status.py

@@ -0,0 +1,26 @@
+"""add message status column
+
+Revision ID: 0009
+Revises: 0008
+Create Date: 2026-02-11 00:00:00.000000
+"""
+
+from alembic import op
+
+revision = "0009"
+down_revision = "0008"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.execute("""
+        DO $$ BEGIN
+            ALTER TABLE messages ADD COLUMN status TEXT NOT NULL DEFAULT 'complete';
+        EXCEPTION WHEN duplicate_column THEN NULL;
+        END $$
+    """)
+
+
+def downgrade() -> None:
+    op.execute("ALTER TABLE messages DROP COLUMN IF EXISTS status")