fusion_claims: cap MOD follow-up email flood with rolling 30-day window

Two daily MOD crons were fighting each other. _cron_mod_schedule_followups
created a mail.activity on every MOD order in quote_submitted/awaiting_funding;
_cron_mod_escalate_followups unconditionally deleted the activity after
sending its one-time reminder email. The activity was recreated every day
in a tight loop with no per-period cap — a legitimate 2-4 month wait for
a MOD funding decision would generate dozens of activity churn events and
a bulk email burst the first time the escalate cron ran against a backlog.

Fix:
- New fields x_fc_mod_followup_month_count / _month_start / _cap_notified
  (copy=False) track a rolling window per order.
- New config params mod_followup_max_per_month (default 2),
  mod_followup_window_days (30), mod_followup_max_per_cron_run (10).
- _send_mod_followup_email resets the window after 30 days, refuses to
  send past the cap, and posts a one-shot chatter note explaining why.
- _cron_mod_schedule_followups no longer recreates the activity when the
  cap has been hit and stops daily-bumping x_fc_mod_next_followup_date.
- _cron_mod_escalate_followups processes oldest-deadline-first with a
  per-run throttle, only unlinks the activity on a successful send so
  humans can still action capped cases manually.
- write() resets the rolling counters on any real MOD status change.

Deployed to fusion_claims v19.0.8.0.1 on odoo-westin (westin-v19,
36 affected orders) and odoo-mobility (mobility, 2 affected orders).

fusion_claims/data/ir_config_parameter_data.xml

@@ -116,6 +116,22 @@
             <field name="key">fusion_claims.mod_followup_escalation_days</field>
             <field name="value">3</field>
         </record>
+        <!-- Hard cap on auto follow-up emails per order per 30-day window. -->
+        <record id="config_mod_followup_max_per_month" model="ir.config_parameter">
+            <field name="key">fusion_claims.mod_followup_max_per_month</field>
+            <field name="value">2</field>
+        </record>
+        <record id="config_mod_followup_window_days" model="ir.config_parameter">
+            <field name="key">fusion_claims.mod_followup_window_days</field>
+            <field name="value">30</field>
+        </record>
+        <!-- Per-cron-run throttle so a backlog of stale MOD cases cannot
+             blast 30+ emails in one minute. Remaining orders roll over to
+             the next day's cron run. -->
+        <record id="config_mod_followup_max_per_cron_run" model="ir.config_parameter">
+            <field name="key">fusion_claims.mod_followup_max_per_cron_run</field>
+            <field name="value">10</field>
+        </record>
 
         <!-- ODSP Settings -->
         <record id="config_sa_mobility_email" model="ir.config_parameter">