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

frontend/src/routes/migration/+page.svelte

@@ -0,0 +1,132 @@
+<!-- [DEF:MigrationDashboard:Component] -->
+<!--
+@SEMANTICS: migration, dashboard, environment, selection, database-replacement
+@PURPOSE:   Main dashboard for configuring and starting migrations.
+@LAYER:     Page
+@RELATION:  USES -> EnvSelector
+
+@INVARIANT: Migration cannot start without source and target environments.
+-->
+
+<script lang="ts">
+  // [SECTION: IMPORTS]
+  import { onMount } from 'svelte';
+  import EnvSelector from '../../components/EnvSelector.svelte';
+  // [/SECTION]
+
+  // [SECTION: STATE]
+  let environments = [];
+  let sourceEnvId = "";
+  let targetEnvId = "";
+  let dashboardRegex = ".*";
+  let replaceDb = false;
+  let loading = true;
+  let error = "";
+  // [/SECTION]
+
+  // [DEF:fetchEnvironments:Function]
+  /**
+   * @purpose Fetches the list of environments from the API.
+   * @post    environments state is updated.
+   */
+  async function fetchEnvironments() {
+    try {
+      const response = await fetch('/api/environments');
+      if (!response.ok) throw new Error('Failed to fetch environments');
+      environments = await response.json();
+    } catch (e) {
+      error = e.message;
+    } finally {
+      loading = false;
+    }
+  }
+  // [/DEF:fetchEnvironments]
+
+  onMount(fetchEnvironments);
+
+  // [DEF:startMigration:Function]
+  /**
+   * @purpose Starts the migration process.
+   * @pre     sourceEnvId and targetEnvId must be set and different.
+   */
+  async function startMigration() {
+    if (!sourceEnvId || !targetEnvId) {
+      error = "Please select both source and target environments.";
+      return;
+    }
+    if (sourceEnvId === targetEnvId) {
+      error = "Source and target environments must be different.";
+      return;
+    }
+    
+    error = "";
+    console.log(`[MigrationDashboard][Action] Starting migration from ${sourceEnvId} to ${targetEnvId} (Replace DB: ${replaceDb})`);
+    // TODO: Implement actual migration trigger in US3
+  }
+  // [/DEF:startMigration]
+</script>
+
+<!-- [SECTION: TEMPLATE] -->
+<div class="max-w-4xl mx-auto p-6">
+  <h1 class="text-2xl font-bold mb-6">Migration Dashboard</h1>
+
+  {#if loading}
+    <p>Loading environments...</p>
+  {:else if error}
+    <div class="bg-red-100 border border-red-400 text-red-700 px-4 py-3 rounded mb-4">
+      {error}
+    </div>
+  {/if}
+
+  <div class="grid grid-cols-1 md:grid-cols-2 gap-6 mb-8">
+    <EnvSelector
+      label="Source Environment"
+      bind:selectedId={sourceEnvId}
+      {environments}
+    />
+    <EnvSelector
+      label="Target Environment"
+      bind:selectedId={targetEnvId}
+      {environments}
+    />
+  </div>
+
+  <div class="mb-8">
+    <label for="dashboard-regex" class="block text-sm font-medium text-gray-700 mb-1">Dashboard Regex</label>
+    <input
+      id="dashboard-regex"
+      type="text"
+      bind:value={dashboardRegex}
+      placeholder="e.g. ^Finance Dashboard$"
+      class="shadow-sm focus:ring-indigo-500 focus:border-indigo-500 block w-full sm:text-sm border-gray-300 rounded-md"
+    />
+    <p class="mt-1 text-sm text-gray-500">Regular expression to filter dashboards to migrate.</p>
+  </div>
+
+  <div class="flex items-center mb-8">
+    <input
+      id="replace-db"
+      type="checkbox"
+      bind:checked={replaceDb}
+      class="h-4 w-4 text-indigo-600 focus:ring-indigo-500 border-gray-300 rounded"
+    />
+    <label for="replace-db" class="ml-2 block text-sm text-gray-900">
+      Replace Database (Apply Mappings)
+    </label>
+  </div>
+
+  <button
+    on:click={startMigration}
+    disabled={!sourceEnvId || !targetEnvId || sourceEnvId === targetEnvId}
+    class="inline-flex items-center px-4 py-2 border border-transparent text-sm font-medium rounded-md shadow-sm text-white bg-indigo-600 hover:bg-indigo-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500 disabled:bg-gray-400"
+  >
+    Start Migration
+  </button>
+</div>
+<!-- [/SECTION] -->
+
+<style>
+  /* Page specific styles */
+</style>
+
+<!-- [/DEF:MigrationDashboard] -->