feat: add recurring invoices, public links, time tracker, payments, reminders

- Recurring invoices: schedule-based auto-generation with CRUD UI at /dashboard/invoices/recurring and POST /api/cron/generate-recurring cron endpoint
- Public invoice link: generate/revoke shareable /i/[token] page for unauthenticated clients with PDF download
- Live time tracker: localStorage-persisted timer widget in invoice editor that appends a line item on stop (rounds to nearest 0.25h)
- Partial payment tracking: record payments per invoice, auto-mark paid when fully covered, balance due display
- Send reminder: email reminder via Resend with custom message dialog and last-sent indicator

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/server/api/routers/payments.ts

@@ -0,0 +1,103 @@
+import { z } from "zod";
+import { eq, sum } from "drizzle-orm";
+import { createTRPCRouter, protectedProcedure } from "../trpc";
+import { invoicePayments, invoices } from "~/server/db/schema";
+import { TRPCError } from "@trpc/server";
+
+const PAYMENT_METHODS = ["cash", "check", "bank_transfer", "credit_card", "paypal", "other"] as const;
+
+export const paymentsRouter = createTRPCRouter({
+  getByInvoice: protectedProcedure
+    .input(z.object({ invoiceId: z.string() }))
+    .query(async ({ ctx, input }) => {
+      const invoice = await ctx.db.query.invoices.findFirst({
+        where: eq(invoices.id, input.invoiceId),
+      });
+      if (invoice?.createdById !== ctx.session.user.id) {
+        throw new TRPCError({ code: "NOT_FOUND" });
+      }
+      return ctx.db.query.invoicePayments.findMany({
+        where: eq(invoicePayments.invoiceId, input.invoiceId),
+        orderBy: (p, { desc }) => [desc(p.date)],
+      });
+    }),
+
+  create: protectedProcedure
+    .input(
+      z.object({
+        invoiceId: z.string(),
+        amount: z.number().positive(),
+        date: z.date(),
+        method: z.enum(PAYMENT_METHODS).default("other"),
+        notes: z.string().max(500).optional(),
+      }),
+    )
+    .mutation(async ({ ctx, input }) => {
+      const invoice = await ctx.db.query.invoices.findFirst({
+        where: eq(invoices.id, input.invoiceId),
+      });
+      if (invoice?.createdById !== ctx.session.user.id) {
+        throw new TRPCError({ code: "NOT_FOUND" });
+      }
+
+      await ctx.db.insert(invoicePayments).values({
+        invoiceId: input.invoiceId,
+        amount: input.amount,
+        currency: invoice.currency,
+        date: input.date,
+        method: input.method,
+        notes: input.notes ?? null,
+        createdById: ctx.session.user.id,
+      });
+
+      // Auto-mark paid if total payments >= invoice total
+      const [totals] = await ctx.db
+        .select({ paid: sum(invoicePayments.amount) })
+        .from(invoicePayments)
+        .where(eq(invoicePayments.invoiceId, input.invoiceId));
+
+      const totalPaid = Number(totals?.paid ?? 0);
+      if (totalPaid >= invoice.totalAmount && invoice.status !== "paid") {
+        await ctx.db
+          .update(invoices)
+          .set({ status: "paid" })
+          .where(eq(invoices.id, input.invoiceId));
+      }
+
+      return { success: true };
+    }),
+
+  delete: protectedProcedure
+    .input(z.object({ id: z.string() }))
+    .mutation(async ({ ctx, input }) => {
+      const payment = await ctx.db.query.invoicePayments.findFirst({
+        where: eq(invoicePayments.id, input.id),
+      });
+      if (!payment) throw new TRPCError({ code: "NOT_FOUND" });
+
+      const invoice = await ctx.db.query.invoices.findFirst({
+        where: eq(invoices.id, payment.invoiceId),
+      });
+      if (invoice?.createdById !== ctx.session.user.id) {
+        throw new TRPCError({ code: "FORBIDDEN" });
+      }
+
+      await ctx.db.delete(invoicePayments).where(eq(invoicePayments.id, input.id));
+
+      // Re-check paid status after deletion
+      const [totals] = await ctx.db
+        .select({ paid: sum(invoicePayments.amount) })
+        .from(invoicePayments)
+        .where(eq(invoicePayments.invoiceId, payment.invoiceId));
+
+      const totalPaid = Number(totals?.paid ?? 0);
+      if (totalPaid < invoice.totalAmount && invoice.status === "paid") {
+        await ctx.db
+          .update(invoices)
+          .set({ status: "sent" })
+          .where(eq(invoices.id, payment.invoiceId));
+      }
+
+      return { success: true };
+    }),
+});