fix(6229): remove the Profile settings page — nothing read it

The Profile tab said an assistant used it to personalise chat and a daily
journal. Neither exists, and nothing read the profile: the page saved to
user_profiles and the backup carried it. Removed the tab, the client calls,
/api/profile, the service and the model, and migration 0123 drops the table
(downgrade recreates it empty).

Backup format v27 stops writing user_profiles; an older archive carrying the
section still restores, and the file-restore integration test now proves it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

alembic/versions/0123_drop_user_profiles.py

@@ -0,0 +1,64 @@
+"""drop user_profiles
+
+Revision ID: 0123
+Revises: 0122
+Create Date: 2026-10-22
+
+The Profile settings page asked for a display name, job title, expertise,
+response style, tone, interests and a work schedule, and said an assistant
+used them to personalise chat and a daily journal. Nothing in the app read
+any of it: the page saved to this table and the backup carried it, and that
+was all. The page, its API and the backup section are gone, and the table
+goes with them.
+
+Downgrade recreates the empty table, so the schema steps back cleanly; the
+rows themselves do not come back.
+"""
+import sqlalchemy as sa
+from alembic import op
+from sqlalchemy.dialects.postgresql import ARRAY, JSONB
+
+revision = "0123"
+down_revision = "0122"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.drop_index("ix_user_profiles_user_id", table_name="user_profiles")
+    op.drop_table("user_profiles")
+
+
+def downgrade() -> None:
+    op.create_table(
+        "user_profiles",
+        sa.Column("id", sa.Integer(), primary_key=True),
+        sa.Column(
+            "user_id",
+            sa.Integer(),
+            sa.ForeignKey("users.id", ondelete="CASCADE"),
+            nullable=False,
+            unique=True,
+        ),
+        sa.Column("display_name", sa.Text(), nullable=True),
+        sa.Column("job_title", sa.Text(), nullable=True),
+        sa.Column("industry", sa.Text(), nullable=True),
+        sa.Column("expertise_level", sa.Text(), nullable=True),
+        sa.Column("response_style", sa.Text(), nullable=True),
+        sa.Column("tone", sa.Text(), nullable=True),
+        sa.Column("interests", ARRAY(sa.Text()), nullable=True),
+        sa.Column("work_schedule", JSONB(), nullable=True),
+        sa.Column(
+            "created_at",
+            sa.DateTime(timezone=True),
+            server_default=sa.func.now(),
+            nullable=False,
+        ),
+        sa.Column(
+            "updated_at",
+            sa.DateTime(timezone=True),
+            server_default=sa.func.now(),
+            nullable=False,
+        ),
+    )
+    op.create_index("ix_user_profiles_user_id", "user_profiles", ["user_id"], unique=True)