feat: Add decoupled pipeline schema with separate PostgreSQL namespace

- Create consolidated migration (005_create_pipeline_schema.sql) with
  'pipeline' schema for all classification tables
- Update pipeline repositories to use schema prefix (pipeline.*)
- Add run_migrations() method to DatabaseManager
- Add CLI tool for running versioned migrations

Tables created in pipeline schema:
- reviews_raw, reviews_enriched (Stage 1)
- review_spans (Stage 2)
- issues, issue_spans, issue_events (Stage 3)
- fact_timeseries (Stage 4)
- urt_domains, urt_categories (taxonomy lookup)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tools/run_migrations.py

@@ -0,0 +1,76 @@
+#!/usr/bin/env python3
+"""
+CLI tool to run database migrations.
+
+Usage:
+    python tools/run_migrations.py --database-url $DATABASE_URL
+
+    # Or with environment variable
+    export DATABASE_URL=postgresql://user:pass@localhost/db
+    python tools/run_migrations.py
+"""
+
+import asyncio
+import os
+import sys
+import argparse
+import logging
+
+# Add project root to path
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
+
+from core.database import DatabaseManager
+
+logging.basicConfig(
+    level=logging.INFO,
+    format="%(asctime)s - %(name)s - %(levelname)s - %(message)s",
+)
+
+
+async def main(database_url: str, migrations_dir: str = "migrations/versions"):
+    """Run migrations against the database."""
+    db = DatabaseManager(database_url)
+
+    try:
+        await db.connect()
+
+        # First initialize base schema (jobs table, etc.)
+        print("Initializing base schema...")
+        await db.initialize_schema()
+
+        # Then run versioned migrations
+        print(f"\nRunning migrations from {migrations_dir}...")
+        count = await db.run_migrations(migrations_dir)
+
+        if count > 0:
+            print(f"\n✓ Applied {count} migration(s)")
+        else:
+            print("\n✓ No pending migrations")
+
+    except Exception as e:
+        print(f"\n✗ Migration failed: {e}", file=sys.stderr)
+        sys.exit(1)
+    finally:
+        await db.disconnect()
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Run database migrations")
+    parser.add_argument(
+        "--database-url",
+        default=os.environ.get("DATABASE_URL"),
+        help="PostgreSQL connection string (default: $DATABASE_URL)",
+    )
+    parser.add_argument(
+        "--migrations-dir",
+        default="migrations/versions",
+        help="Directory containing .sql migration files",
+    )
+
+    args = parser.parse_args()
+
+    if not args.database_url:
+        print("Error: --database-url required or set DATABASE_URL environment variable", file=sys.stderr)
+        sys.exit(1)
+
+    asyncio.run(main(args.database_url, args.migrations_dir))