refactor(db): migrate interview preparation

Move durable user-owned interview preparation into an additive provider-aware migration. Preserve questions, answers, practice state, ordering, and application cascade semantics.

JobTrackerApi/Migrations/20260830132000_AdoptInterviewPrepItemSchema.cs

@@ -0,0 +1,70 @@
+using System;
+using JobTrackerApi.Data;
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace JobTrackerApi.Migrations;
+
+/// <summary>
+/// Moves durable user-owned interview preparation into migration ownership without replacing
+/// questions, answers, research, or practice state.
+/// </summary>
+[DbContext(typeof(JobTrackerContext))]
+[Migration("20260830132000_AdoptInterviewPrepItemSchema")]
+public sealed class AdoptInterviewPrepItemSchema : Migration
+{
+    protected override void Up(MigrationBuilder migrationBuilder)
+    {
+        if (ActiveProvider.Contains("MySql", StringComparison.OrdinalIgnoreCase))
+        {
+            migrationBuilder.Sql("""
+                CREATE TABLE IF NOT EXISTS `InterviewPrepItems` (
+                    `Id` int NOT NULL AUTO_INCREMENT,
+                    `OwnerUserId` varchar(255) NOT NULL,
+                    `JobApplicationId` int NOT NULL,
+                    `Category` varchar(32) NOT NULL,
+                    `Title` varchar(500) NOT NULL,
+                    `Content` longtext NULL,
+                    `Source` varchar(16) NOT NULL,
+                    `IsPrepared` tinyint(1) NOT NULL,
+                    `SortOrder` int NOT NULL,
+                    `CreatedAtUtc` datetime(6) NOT NULL,
+                    `UpdatedAtUtc` datetime(6) NOT NULL,
+                    PRIMARY KEY (`Id`),
+                    CONSTRAINT `FK_InterviewPrepItems_JobApplications_JobApplicationId`
+                        FOREIGN KEY (`JobApplicationId`) REFERENCES `JobApplications` (`Id`) ON DELETE CASCADE
+                ) CHARACTER SET=utf8mb4;
+                CREATE INDEX IF NOT EXISTS `IX_InterviewPrepItems_Owner_Job_Sort`
+                    ON `InterviewPrepItems` (`OwnerUserId`, `JobApplicationId`, `SortOrder`);
+                """);
+            return;
+        }
+
+        migrationBuilder.Sql("""
+            CREATE TABLE IF NOT EXISTS "InterviewPrepItems" (
+                "Id" INTEGER NOT NULL CONSTRAINT "PK_InterviewPrepItems" PRIMARY KEY AUTOINCREMENT,
+                "OwnerUserId" TEXT NOT NULL,
+                "JobApplicationId" INTEGER NOT NULL,
+                "Category" TEXT NOT NULL,
+                "Title" TEXT NOT NULL,
+                "Content" TEXT NULL,
+                "Source" TEXT NOT NULL,
+                "IsPrepared" INTEGER NOT NULL,
+                "SortOrder" INTEGER NOT NULL,
+                "CreatedAtUtc" TEXT NOT NULL,
+                "UpdatedAtUtc" TEXT NOT NULL,
+                CONSTRAINT "FK_InterviewPrepItems_JobApplications_JobApplicationId"
+                    FOREIGN KEY ("JobApplicationId") REFERENCES "JobApplications" ("Id") ON DELETE CASCADE
+            );
+            CREATE INDEX IF NOT EXISTS "IX_InterviewPrepItems_Owner_Job_Sort"
+                ON "InterviewPrepItems" ("OwnerUserId", "JobApplicationId", "SortOrder");
+            """);
+    }
+
+    protected override void Down(MigrationBuilder migrationBuilder)
+    {
+        // Preserve durable user-authored preparation from pre-migration installations.
+    }
+}

JobTrackerApi/Models/InterviewPrepItem.cs

@@ -8,8 +8,7 @@ namespace JobTrackerApi.Models;
 // own questions — and nothing regenerates it.
 //
 // One table for every category rather than a table per category: they differ only by label, and a new
-// category must not need a migration. Reconciler-owned
-// (docs/infrastructure/database-ownership.md); its migration is a no-op.
+// category must not need a migration. Migration-owned through an additive provider-aware adoption.
 public sealed class InterviewPrepItem
 {
     public int Id { get; set; }

JobTrackerApi/Services/StartupInitializationExtensions.cs

@@ -712,32 +712,9 @@ public static class StartupInitializationExtensions
                     EnsureColumn(c, "AiInteractions", "EstimatedTokenCount", "ALTER TABLE AiInteractions ADD COLUMN EstimatedTokenCount INTEGER NOT NULL DEFAULT 0;");
                 }
 
-                // Phase 5.5: user-owned interview preparation (not the AI cache InterviewPrepNote).
-                static void EnsureInterviewPrepItemsTable(DbConnection c)
-                {
-                    Exec(c, """
-        CREATE TABLE IF NOT EXISTS "InterviewPrepItems" (
-            "Id" INTEGER NOT NULL CONSTRAINT "PK_InterviewPrepItems" PRIMARY KEY AUTOINCREMENT,
-            "OwnerUserId" TEXT NOT NULL,
-            "JobApplicationId" INTEGER NOT NULL,
-            "Category" TEXT NOT NULL,
-            "Title" TEXT NOT NULL,
-            "Content" TEXT NULL,
-            "Source" TEXT NOT NULL,
-            "IsPrepared" INTEGER NOT NULL,
-            "SortOrder" INTEGER NOT NULL,
-            "CreatedAtUtc" TEXT NOT NULL,
-            "UpdatedAtUtc" TEXT NOT NULL,
-            CONSTRAINT "FK_InterviewPrepItems_JobApplications_JobApplicationId" FOREIGN KEY ("JobApplicationId") REFERENCES "JobApplications" ("Id") ON DELETE CASCADE
-        );
-        """);
-                    Exec(c, """CREATE INDEX IF NOT EXISTS "IX_InterviewPrepItems_Owner_Job_Sort" ON "InterviewPrepItems" ("OwnerUserId", "JobApplicationId", "SortOrder");""");
-                }
-
                 ReconcileGmailConnectionColumns(conn);
                 EnsureCareerProfileTables(conn);
                 ReconcileAiInteractionUsageColumns(conn);
-                EnsureInterviewPrepItemsTable(conn);
 
                 // Once the base app tables exist, provision this reconciler-owned schema set and
                 // stamp its historical migration before later migrations rebuild JobApplications.
@@ -1131,27 +1108,6 @@ public static class StartupInitializationExtensions
                     DropMalformedMySqlTable(conn, "CoverLetterVersions", "CreatedAtUtc", "datetime");
                     DropMalformedMySqlTable(conn, "InterviewPrepItems", "CreatedAtUtc", "datetime");
 
-                    if (!HasMySqlTable(conn, "InterviewPrepItems") && HasMySqlTable(conn, "JobApplications"))
-                    {
-                        using var cmd = conn.CreateCommand();
-                        cmd.CommandText = @"CREATE TABLE IF NOT EXISTS `InterviewPrepItems` (
-        `Id` int NOT NULL AUTO_INCREMENT,
-        `OwnerUserId` varchar(255) NOT NULL,
-        `JobApplicationId` int NOT NULL,
-        `Category` varchar(32) NOT NULL,
-        `Title` varchar(500) NOT NULL,
-        `Content` longtext NULL,
-        `Source` varchar(16) NOT NULL,
-        `IsPrepared` tinyint(1) NOT NULL,
-        `SortOrder` int NOT NULL,
-        `CreatedAtUtc` datetime(6) NOT NULL,
-        `UpdatedAtUtc` datetime(6) NOT NULL,
-        PRIMARY KEY (`Id`),
-        CONSTRAINT `FK_InterviewPrepItems_JobApplications_JobApplicationId` FOREIGN KEY (`JobApplicationId`) REFERENCES `JobApplications` (`Id`) ON DELETE CASCADE
-        );";
-                        cmd.ExecuteNonQuery();
-                    }
-
                     EnsureMySqlAutoIncrementPrimaryKey(conn, "InterviewPrepItems", "Id");
                     EnsureMySqlIndex(conn, "InterviewPrepItems", "IX_InterviewPrepItems_Owner_Job_Sort", "`OwnerUserId`, `JobApplicationId`, `SortOrder`");
 

JobTrackerApi/Services/StartupSchemaOwnership.cs

@@ -29,6 +29,7 @@ internal static class StartupSchemaOwnership
         "GmailReviewDecisions",
         "ImapConnections",
         "InterviewPrepNotes",
+        "InterviewPrepItems",
         "JobApplications",
         "JobEvents",
         "Jobs",
@@ -61,7 +62,6 @@ internal static class StartupSchemaOwnership
         "CareerProfileVersions",
         "CareerProjects",
         "CareerSkills",
-        "InterviewPrepItems",
     };
 
     // Historical migrations contain guarded compatibility bootstraps for these tables so direct