fix(db): provision CV builder + AI workspace tables via the MySQL-safe reconciler

Deploy failed on prod (MariaDB) while the test job was green: backend startup
threw during Database.Migrate(), so deploy.sh's post-deploy health check exited.

Root cause: AddCvVariants/AddAiInteractions were scaffolded against SQLite, so
they bake SQLite type names into their DDL — DateTimeOffset emits `TEXT`, bool/int
emit `INTEGER`, and the PK gets no AUTO_INCREMENT. Run against MariaDB that yields
a structurally wrong table, and the composite index over a TEXT column then trips
"ERROR 1071: Specified key was too long; max key length is 3072 bytes". SQLite
accepts all of it, which is why local/container verification passed.

Fix, following the pattern already used for CareerProfiles/AiWorkspaceNotes:
- both migrations become no-ops; the three tables are reconciler-owned
- reconciler provisions them idempotently per dialect (MySQL: varchar/int
  AUTO_INCREMENT/datetime(6); SQLite: CREATE TABLE IF NOT EXISTS)
- DropMalformedMySqlTable rebuilds a half-built table left by the failed
  migration, guarded on row count so a table with ANY rows is never dropped
- bound the indexed string columns with HasMaxLength so the model matches

Verified against a real MariaDB 11 container: reproduced error 1071, then
confirmed the corrected DDL yields auto_increment PKs, varchar/datetime columns
and all previously-failing indexes. 306 backend tests green; SQLite container
starts clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

JobTrackerApi/Migrations/20260718131138_AddAiInteractions.cs

@@ -8,51 +8,18 @@ namespace JobTrackerApi.Migrations
     /// <inheritdoc />
     public partial class AddAiInteractions : Migration
     {
+        // Intentionally a no-op — AiInteractions is provisioned by the reconciler in
+        // StartupInitializationExtensions (idempotent, MySQL-safe: Module/OwnerUserId are varchar so
+        // MariaDB can index them). The original CREATE INDEX here indexed unbounded string columns,
+        // which crashes backend startup on MariaDB. See the AddCvVariants migration for the full note.
         /// <inheritdoc />
         protected override void Up(MigrationBuilder migrationBuilder)
         {
-            migrationBuilder.CreateTable(
-                name: "AiInteractions",
-                columns: table => new
-                {
-                    Id = table.Column<int>(type: "INTEGER", nullable: false)
-                        .Annotation("Sqlite:Autoincrement", true),
-                    OwnerUserId = table.Column<string>(type: "TEXT", nullable: false),
-                    JobApplicationId = table.Column<int>(type: "INTEGER", nullable: false),
-                    Module = table.Column<string>(type: "TEXT", nullable: false),
-                    Mode = table.Column<string>(type: "TEXT", nullable: true),
-                    Title = table.Column<string>(type: "TEXT", nullable: false),
-                    Provider = table.Column<string>(type: "TEXT", nullable: false),
-                    ResultJson = table.Column<string>(type: "TEXT", nullable: false),
-                    CreatedAtUtc = table.Column<DateTimeOffset>(type: "TEXT", nullable: false)
-                },
-                constraints: table =>
-                {
-                    table.PrimaryKey("PK_AiInteractions", x => x.Id);
-                    table.ForeignKey(
-                        name: "FK_AiInteractions_JobApplications_JobApplicationId",
-                        column: x => x.JobApplicationId,
-                        principalTable: "JobApplications",
-                        principalColumn: "Id",
-                        onDelete: ReferentialAction.Cascade);
-                });
-
-            migrationBuilder.CreateIndex(
-                name: "IX_AiInteractions_JobApplicationId",
-                table: "AiInteractions",
-                column: "JobApplicationId");
-
-            migrationBuilder.CreateIndex(
-                name: "IX_AiInteractions_OwnerUserId_JobApplicationId_Module_CreatedAtUtc",
-                table: "AiInteractions",
-                columns: new[] { "OwnerUserId", "JobApplicationId", "Module", "CreatedAtUtc" });
         }
 
         /// <inheritdoc />
         protected override void Down(MigrationBuilder migrationBuilder)
         {
-            migrationBuilder.DropTable(
-                name: "AiInteractions");
         }
     }
 }