feat(migration): implement interactive mapping resolution workflow

- Add SQLite database integration for environments and mappings
- Update TaskManager to support pausing tasks (AWAITING_MAPPING)
- Modify MigrationPlugin to detect missing mappings and wait for resolution
- Add frontend UI for handling missing mappings interactively
- Create dedicated migration routes and API endpoints
- Update .gitignore and project documentation

specs/001-migration-ui-redesign/plan.md

@@ -0,0 +1,79 @@
+# Implementation Plan: Migration Process and UI Redesign
+
+**Branch**: `001-migration-ui-redesign` | **Date**: 2025-12-20 | **Spec**: [specs/001-migration-ui-redesign/spec.md](specs/001-migration-ui-redesign/spec.md)
+
+## Summary
+
+Redesign the migration process to support environment-based selection and automated database mapping. The technical approach involves using a SQLite database to persist mappings between source and target databases, implementing a fuzzy matching algorithm for empirical suggestions, and intercepting asset definitions during migration to apply these mappings.
+
+## Technical Context
+
+**Language/Version**: Python 3.9+, Node.js 18+  
+**Primary Dependencies**: FastAPI, SvelteKit, Tailwind CSS, Pydantic, SQLite  
+**Storage**: SQLite (for database mappings and environment metadata)  
+**Testing**: pytest (Backend), Vitest/Playwright (Frontend)  
+**Target Platform**: Linux server  
+**Project Type**: Web application (FastAPI + SvelteKit SPA)  
+**Performance Goals**: SC-001: Users can complete a full database mapping for 5+ databases in under 60 seconds.  
+**Constraints**: SPA-First Architecture (Constitution Principle I), API-Driven Communication (Constitution Principle II).  
+**Scale/Scope**: Support for multiple environments and hundreds of database mappings.
+
+## Constitution Check
+
+*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*
+
+| Principle | Status | Notes |
+|-----------|--------|-------|
+| I. SPA-First Architecture | PASS | SvelteKit will be built as a static SPA and served by FastAPI. |
+| II. API-Driven Communication | PASS | All mapping and migration actions will go through FastAPI endpoints. |
+| III. Modern Stack Consistency | PASS | Using FastAPI, SvelteKit, and Tailwind CSS. |
+| IV. Semantic Protocol Adherence | PASS | Code will include GRACE-Poly anchors and contracts. |
+
+## Project Structure
+
+### Documentation (this feature)
+
+```text
+specs/001-migration-ui-redesign/
+├── plan.md              # This file
+├── research.md          # Phase 0 output
+├── data-model.md        # Phase 1 output
+├── quickstart.md        # Phase 1 output
+├── contracts/           # Phase 1 output
+└── tasks.md             # Phase 2 output
+```
+
+### Source Code (repository root)
+
+```text
+backend/
+├── src/
+│   ├── api/
+│   │   └── routes/
+│   │       ├── environments.py  # New: Env selection
+│   │       └── mappings.py      # New: DB mapping management
+│   ├── core/
+│   │   └── migration_engine.py  # Update: DB replacement logic
+│   └── models/
+│       └── mapping.py           # New: SQLite models
+└── tests/
+
+frontend/
+├── src/
+│   ├── components/
+│   │   ├── MappingTable.svelte  # New: DB mapping UI
+│   │   └── EnvSelector.svelte   # New: Source/Target selection
+│   └── routes/
+│       └── migration/           # New: Migration dashboard
+└── tests/
+```
+
+**Structure Decision**: Web application structure (Option 2) is selected to maintain separation between the FastAPI backend and SvelteKit frontend while adhering to the SPA-first principle.
+
+## Complexity Tracking
+
+> **Fill ONLY if Constitution Check has violations that must be justified**
+
+| Violation | Why Needed | Simpler Alternative Rejected Because |
+|-----------|------------|-------------------------------------|
+| None | N/A | N/A |