feat: Add extensible multi-pipeline integration system

This commit implements a plugin-like pipeline architecture with:

Pipeline Core Package (packages/pipeline-core/):
- BasePipeline abstract class all pipelines implement
- PipelineRegistry for database-backed discovery/management
- PipelineRunner for execution with status tracking
- DashboardConfig contracts for dynamic widget definitions

Database Migration (006_pipeline_registry.sql):
- pipeline.registry table for registered pipelines
- pipeline.executions table for execution history
- Views for execution stats and monitoring

ReviewIQ Pipeline Refactor:
- Implements BasePipeline interface
- Adds get_dashboard_config() with widget definitions
- Adds get_widget_data() methods for all dashboard widgets
- Maintains backward compatibility with Pipeline alias

Generic Pipeline API (api/routes/pipelines.py):
- GET /api/pipelines - List all registered pipelines
- GET /api/pipelines/{id} - Pipeline details
- POST /api/pipelines/{id}/execute - Execute pipeline
- GET /api/pipelines/{id}/dashboard - Dashboard config
- GET /api/pipelines/{id}/widgets/{w} - Widget data
- GET /api/pipelines/{id}/executions - Execution history

Frontend Dynamic Dashboard System:
- DynamicDashboard component renders from config
- WidgetRegistry maps types to components
- Widget components: StatCard, LineChart, BarChart,
  PieChart, DataTable, Heatmap
- Pipeline API client library

Frontend Pipeline Pages:
- /pipelines - List all registered pipelines
- /pipelines/[id] - Dynamic dashboard for pipeline
- /pipelines/[id]/executions - Execution history
- Pipelines nav item in Sidebar

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

packages/reviewiq-pipeline/src/reviewiq_pipeline/__init__.py

@@ -6,6 +6,9 @@ This package provides a complete pipeline for processing customer reviews:
 - Stage 2: LLM Classification (span extraction with URT codes)
 - Stage 3: Issue Routing (route negative spans to issues)
 - Stage 4: Fact Aggregation (pre-aggregate metrics for dashboards)
+
+Implements the BasePipeline interface from pipeline-core for the extensible
+multi-pipeline system with dynamic dashboards.
 """
 
 from reviewiq_pipeline.config import Config
@@ -28,12 +31,14 @@ from reviewiq_pipeline.contracts import (
     ValidationError,
     ValidationResult,
 )
-from reviewiq_pipeline.pipeline import Pipeline
+from reviewiq_pipeline.pipeline import Pipeline, PipelineResult, ReviewIQPipeline
 
 __version__ = "0.1.0"
 __all__ = [
     # Main API
     "Pipeline",
+    "ReviewIQPipeline",
+    "PipelineResult",
     "Config",
     # Contracts
     "ScraperOutput",