Add collector-level event deduplication using content hashes

Replace presentation-layer deduplication with collector-level approach:
- Add event_hash column to messages, advertisements, trace_paths, telemetry tables
- Handlers compute content hashes and skip duplicate events at insertion time
- Use 5-minute time buckets for advertisements and telemetry
- Include Alembic migration for schema changes

alembic/versions/20241206_0001_003_add_event_hash.py

@@ -0,0 +1,67 @@
+"""Add event_hash column to event tables for deduplication
+
+Revision ID: 003
+Revises: 002
+Create Date: 2024-12-06
+
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = "003"
+down_revision: Union[str, None] = "002"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Add event_hash column to messages table
+    op.add_column(
+        "messages",
+        sa.Column("event_hash", sa.String(32), nullable=True),
+    )
+    op.create_index("ix_messages_event_hash", "messages", ["event_hash"])
+
+    # Add event_hash column to advertisements table
+    op.add_column(
+        "advertisements",
+        sa.Column("event_hash", sa.String(32), nullable=True),
+    )
+    op.create_index("ix_advertisements_event_hash", "advertisements", ["event_hash"])
+
+    # Add event_hash column to trace_paths table
+    op.add_column(
+        "trace_paths",
+        sa.Column("event_hash", sa.String(32), nullable=True),
+    )
+    op.create_index("ix_trace_paths_event_hash", "trace_paths", ["event_hash"])
+
+    # Add event_hash column to telemetry table
+    op.add_column(
+        "telemetry",
+        sa.Column("event_hash", sa.String(32), nullable=True),
+    )
+    op.create_index("ix_telemetry_event_hash", "telemetry", ["event_hash"])
+
+
+def downgrade() -> None:
+    # Remove event_hash from telemetry
+    op.drop_index("ix_telemetry_event_hash", table_name="telemetry")
+    op.drop_column("telemetry", "event_hash")
+
+    # Remove event_hash from trace_paths
+    op.drop_index("ix_trace_paths_event_hash", table_name="trace_paths")
+    op.drop_column("trace_paths", "event_hash")
+
+    # Remove event_hash from advertisements
+    op.drop_index("ix_advertisements_event_hash", table_name="advertisements")
+    op.drop_column("advertisements", "event_hash")
+
+    # Remove event_hash from messages
+    op.drop_index("ix_messages_event_hash", table_name="messages")
+    op.drop_column("messages", "event_hash")