feat(finance): Phase 4 — Tags

- tags table: name, color; transaction_tags junction table
- GET/POST /api/tags; DELETE /api/tags/:id
- POST/DELETE /api/transactions/:id/tags for per-transaction tagging
- Bulk tag/untag via /api/transactions/bulk (action: tag/untag)
- Tags returned inline with transaction list via LATERAL join
- Tag filter on Transactions page
- Bulk "Tag as..." in bulk action bar
- Tag pills + "+" picker on each transaction row
- /tags page: create with color picker, list with counts, delete

src/app/api/tags/[id]/route.ts

@@ -0,0 +1,8 @@
+import { NextRequest, NextResponse } from "next/server";
+import { queryRaw } from "@/lib/db";
+
+export async function DELETE(_req: NextRequest, { params }: { params: Promise<{ id: string }> }) {
+  const { id } = await params;
+  await queryRaw(`DELETE FROM tags WHERE id = $1`, [Number(id)]);
+  return NextResponse.json({ ok: true });
+}

src/app/api/tags/route.ts

@@ -0,0 +1,20 @@
+import { NextRequest, NextResponse } from "next/server";
+import { getTags } from "@/lib/queries";
+import { queryRaw } from "@/lib/db";
+
+export async function GET() {
+  const tags = await getTags();
+  return NextResponse.json(tags);
+}
+
+export async function POST(req: NextRequest) {
+  const { name, color } = await req.json();
+  if (!name?.trim()) {
+    return NextResponse.json({ error: "name required" }, { status: 400 });
+  }
+  const rows = await queryRaw<{ id: number; name: string; color: string }>(
+    `INSERT INTO tags (name, color) VALUES ($1, $2) RETURNING id, name, color`,
+    [name.trim(), color || "#6366f1"]
+  );
+  return NextResponse.json(rows[0], { status: 201 });
+}

src/app/api/transactions/[id]/tags/route.ts

@@ -0,0 +1,24 @@
+import { NextRequest, NextResponse } from "next/server";
+import { queryRaw } from "@/lib/db";
+
+export async function POST(req: NextRequest, { params }: { params: Promise<{ id: string }> }) {
+  const { id } = await params;
+  const { tag_id } = await req.json();
+  if (!tag_id) return NextResponse.json({ error: "tag_id required" }, { status: 400 });
+  await queryRaw(
+    `INSERT INTO transaction_tags (transaction_id, tag_id) VALUES ($1, $2) ON CONFLICT DO NOTHING`,
+    [Number(id), Number(tag_id)]
+  );
+  return NextResponse.json({ ok: true });
+}
+
+export async function DELETE(req: NextRequest, { params }: { params: Promise<{ id: string }> }) {
+  const { id } = await params;
+  const { tag_id } = await req.json();
+  if (!tag_id) return NextResponse.json({ error: "tag_id required" }, { status: 400 });
+  await queryRaw(
+    `DELETE FROM transaction_tags WHERE transaction_id = $1 AND tag_id = $2`,
+    [Number(id), Number(tag_id)]
+  );
+  return NextResponse.json({ ok: true });
+}

src/app/api/transactions/bulk/route.ts

@@ -1,13 +1,15 @@
 import { NextRequest, NextResponse } from "next/server";
-import { prisma } from "@/lib/db";
+import { prisma, queryRaw } from "@/lib/db";
 
 export async function POST(req: NextRequest) {
   const body = await req.json();
-  const { action, ids, category, merchant_normalized } = body as {
+  const { action, ids, category, merchant_normalized, splits, tag_id } = body as {
     action: string;
     ids: number[];
     category?: string;
     merchant_normalized?: string;
+    splits?: { participant_id: number; share_percent: number }[];
+    tag_id?: number;
   };
 
   if (!ids || !Array.isArray(ids) || ids.length === 0) {
@@ -38,5 +40,42 @@ export async function POST(req: NextRequest) {
     return NextResponse.json({ updated: ids.length });
   }
 
+  if (action === "split" && Array.isArray(splits) && splits.length > 0) {
+    const total = splits.reduce((s, x) => s + x.share_percent, 0);
+    if (Math.abs(total - 100) > 0.01) {
+      return NextResponse.json({ error: "Shares must sum to 100%" }, { status: 400 });
+    }
+    await prisma.$transaction(
+      ids.flatMap((id) => [
+        prisma.transaction_splits.deleteMany({ where: { transaction_id: id } }),
+        prisma.transaction_splits.createMany({
+          data: splits.map((s) => ({
+            transaction_id: id,
+            participant_id: s.participant_id,
+            share_percent: s.share_percent,
+          })),
+        }),
+      ])
+    );
+    return NextResponse.json({ updated: ids.length });
+  }
+
+  if ((action === "tag" || action === "untag") && tag_id) {
+    if (action === "tag") {
+      for (const id of ids) {
+        await queryRaw(
+          `INSERT INTO transaction_tags (transaction_id, tag_id) VALUES ($1, $2) ON CONFLICT DO NOTHING`,
+          [id, tag_id]
+        );
+      }
+    } else {
+      await queryRaw(
+        `DELETE FROM transaction_tags WHERE transaction_id = ANY($1::int[]) AND tag_id = $2`,
+        [ids, tag_id]
+      );
+    }
+    return NextResponse.json({ updated: ids.length });
+  }
+
   return NextResponse.json({ error: "Invalid action" }, { status: 400 });
 }