feat(finance): manual income tracking included in revenue

[Dev869]

Summary

Adds manual income tracking to the Transactions page and rolls it into revenue/income KPIs.

Part 1 — Service layer

• createManualIncome(input) in web/src/services/firestore.ts — writes a transactions doc with provider:'manual', type:'income', isManual:true, positive amount, date, description, category (defaults to Manual Income), ownerId (current uid), createdAt/updatedAt. Mirrors the existing createManualExpense conventions (addDoc + Timestamp). The Transaction model has no client field, so source belongs in description (no model redesign).
• subscribeTransactions(callback) — onSnapshot listener over the user's transactions, mirroring subscribeReceipts.
• useTransactions() hook in web/src/hooks/useFirestore.ts, mirroring useReceipts/useConnectedAccounts.

Part 2 — Transactions page UI

• New web/src/components/finance/AddIncomeModal.tsx, mirroring NewInvoiceModal styling tokens and validation conventions. Fields: amount (required, > 0), date (required, defaults to today), description/source (required), category (optional, defaults to Manual Income).
• "Add Income" button added to the Transactions page header next to "Import CSV"; on submit it calls createManualIncome and refetches the list using the existing pagination refetch pattern.
• Manual income rows surface automatically in the existing list and are visually distinguishable: TransactionRow already renders a "Manual" source badge for provider==='manual' and styles positive amounts (income) green with a + prefix.

Part 3 — Revenue/Dashboard inclusion + double-count rule

• calculateRevenue(items, range, transactions = []) in web/src/lib/finance.ts now adds the sum of manual income transactions (provider==='manual' && type==='income') whose date is in range. Signature is backward compatible (optional transactions defaulting to []).
• Double-count handling: manual income transactions with a matchedWorkItemId are EXCLUDED, since those are tied to an already-counted invoice.
• FinanceOverview.tsx now passes useTransactions() data into calculateRevenue (current and previous period).
• Dashboard.tsx "revenue this month" adds in-range manual income with the same exclusion rule (kept the existing inline invoice predicate untouched to avoid changing invoice behavior).

Constraints respected

No changes to Plaid/Stripe sync, invoice/work-order predicates, routing (no new route — lives on the Transactions page), or unrelated finance logic. Existing styling tokens, TS conventions, and immutable patterns followed. No new dependencies.

Test plan

• cd web && npx tsc -b — exit 0.
• npx vitest run — 75/75 pass (full suite).
• finance.test.ts extended with calculateRevenue cases:
  • in-range manual income added to paid invoices
  • manual income with matchedWorkItemId excluded (double-count guard)
  • out-of-range manual income excluded
  • non-manual / expense transactions ignored
  • backward compatible when no transactions arg passed
• ESLint: no new errors in touched files vs main (pre-existing repo errors unchanged; new files lint clean).
• Manual QA: add income via modal, confirm row appears with Manual badge + green amount, and Finance/Dashboard revenue increases by the entered amount.

[github-actions]

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