New modules (#40)

* new modules

* fix: resolve CodeQL findings on PR #40

- Drop unused json import and unused locals (paid/overdue/tpl) in the
  invoice-email and recurring-invoices tests.
- Remove duplicated ModuleManager import in conftest.py (merge artifact).

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

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: mborchuk

modules/invoice_email/__init__.py

@@ -0,0 +1,64 @@
+{# Invoice view panel — send form + history. Rendered by get_invoice_view_panels. #}
+<div style="margin-top: 20px; border: 1px solid var(--color-border); border-radius: 6px; padding: 15px;">
+    <h3 style="margin-top: 0;">📧 Email this invoice</h3>
+
+    {% if not configured %}
+    <p style="font-size: 13px; color: var(--color-text-muted);">
+        SMTP is not configured yet — set it up in
+        <a href="{{ url_for('settings') }}#invoice_email">Settings → Email</a>.
+    </p>
+    {% else %}
+    <form method="POST" action="{{ url_for('invoice_email.email_send', invoice_id=invoice.id) }}">
+        <div style="display: grid; grid-template-columns: 1fr 2fr; gap: 12px;">
+            <div class="form-group">
+                <label>Recipient</label>
+                <input type="email" name="recipient" required value="{{ recipient }}"
+                       placeholder="customer@example.com">
+            </div>
+            <div class="form-group">
+                <label>Subject</label>
+                <input type="text" name="subject" value="Invoice {invoice_number}">
+            </div>
+        </div>
+        <div class="form-group">
+            <label>Body <small style="color: var(--color-text-muted);">placeholders: {invoice_number} {client_name} {amount} {due_date}</small></label>
+            <textarea name="body" rows="4">Dear {client_name},
+
+Please find attached invoice {invoice_number} for {amount}, due {due_date}.
+
+Best regards</textarea>
+        </div>
+        <button type="submit" class="btn btn-success">Send email</button>
+    </form>
+    {% endif %}
+
+    {% if history %}
+    <h4 style="margin-bottom: 6px;">Send history</h4>
+    <table style="width: 100%; border-collapse: collapse; font-size: 12px;">
+        <thead>
+            <tr>
+                <th style="text-align:left; padding: 4px; border-bottom: 1px solid var(--color-border);">When</th>
+                <th style="text-align:left; padding: 4px; border-bottom: 1px solid var(--color-border);">To</th>
+                <th style="text-align:left; padding: 4px; border-bottom: 1px solid var(--color-border);">Kind</th>
+                <th style="text-align:left; padding: 4px; border-bottom: 1px solid var(--color-border);">Status</th>
+            </tr>
+        </thead>
+        <tbody>
+            {% for log in history %}
+            <tr>
+                <td style="padding: 4px;">{{ log.created_at.strftime('%d/%m/%Y %H:%M') }}</td>
+                <td style="padding: 4px;">{{ log.recipient }}</td>
+                <td style="padding: 4px;">{{ log.kind }}</td>
+                <td style="padding: 4px;">
+                    {% if log.status == 'sent' %}
+                    <span style="color: var(--color-success);">sent</span>
+                    {% else %}
+                    <span style="color: var(--color-danger, red);" title="{{ log.error }}">failed</span>
+                    {% endif %}
+                </td>
+            </tr>
+            {% endfor %}
+        </tbody>
+    </table>
+    {% endif %}
+</div>

modules/invoice_email/index.py

@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+"""
+Cadence math for recurring invoices — pure functions, no Flask, no DB.
+
+CAVEMAN NOTE: keep dumb so tests feed dates and check dates. Monthly and
+quarterly only (per PM scope, closed-ended picker).
+"""
+
+from datetime import date
+
+CADENCES = ('monthly', 'quarterly')
+
+# Safety cap: never materialize more than this many missed periods in one run
+# (protects against a template with next_run_date years in the past).
+MAX_CATCHUP_PERIODS = 12
+
+
+def add_cadence(d, cadence):
+    """Return `d` advanced by one cadence period, clamping the day-of-month.
+
+    Jan 31 + monthly -> Feb 28/29 (clamped), like most billing systems do.
+    """
+    if cadence not in CADENCES:
+        raise ValueError(f'Unknown cadence: {cadence}')
+    months = 1 if cadence == 'monthly' else 3
+    month_index = d.month - 1 + months
+    year = d.year + month_index // 12
+    month = month_index % 12 + 1
+    day = min(d.day, _days_in_month(year, month))
+    return date(year, month, day)
+
+
+def _days_in_month(year, month):
+    if month == 12:
+        nxt = date(year + 1, 1, 1)
+    else:
+        nxt = date(year, month + 1, 1)
+    return (nxt - date(year, month, 1)).days
+
+
+def due_dates(next_run_date, today, cadence):
+    """All period dates due on or before `today`, capped at MAX_CATCHUP_PERIODS.
+
+    Returns (list_of_due_dates, new_next_run_date). Idempotent by construction:
+    caller persists new_next_run_date, so a rerun the same day yields [].
+    """
+    due = []
+    cursor = next_run_date
+    while cursor <= today and len(due) < MAX_CATCHUP_PERIODS:
+        due.append(cursor)
+        cursor = add_cadence(cursor, cadence)
+    return due, cursor