Add export plan guard to block Deye export against plan.

Force PASSIVE/no-export when sell is negative or export_mode is NONE,
and alert NEG_SELL_EXPORT in plan_actual_slot_guard when export still occurs.

Co-authored-by: Cursor <cursoragent@cursor.com>

db/routines/R__076_fn_plan_actual_slot_guard.sql

@@ -24,7 +24,8 @@ as $fn$
       s.interval_start,
       ai.actual_grid_power_w,
       ai.deviation_grid_w,
-      pi.grid_setpoint_w as plan_grid_w
+      pi.grid_setpoint_w as plan_grid_w,
+      pi.effective_sell_price as plan_sell_czk
     from slots s
     inner join ems.audit_interval ai
       on ai.site_id = p_site_id
@@ -41,6 +42,12 @@ as $fn$
       b.deviation_grid_w,
       case
         when b.plan_grid_w is null or b.deviation_grid_w is null then null::text
+        when coalesce(
+            b.plan_sell_czk,
+            ems.fn_effective_sell_price(p_site_id, b.interval_start)
+          ) < 0
+         and coalesce(b.actual_grid_power_w, 0) < -4000
+          then 'NEG_SELL_EXPORT'
         when b.plan_grid_w < -2000 and coalesce(b.actual_grid_power_w, 0) > 2500
           then 'GRID_IMPORT_VS_EXPORT_PLAN'
         when b.plan_grid_w <> 0
@@ -60,6 +67,22 @@ as $fn$
       end as reason_code,
       case
         when b.plan_grid_w is null or b.deviation_grid_w is null then null::text
+        when coalesce(
+            b.plan_sell_czk,
+            ems.fn_effective_sell_price(p_site_id, b.interval_start)
+          ) < 0
+         and coalesce(b.actual_grid_power_w, 0) < -4000
+          then format(
+            'záporná vykupní %s Kč/kWh, skutečnost síť %s W (vývoz nad práh 4 kW)',
+            round(
+              coalesce(
+                b.plan_sell_czk,
+                ems.fn_effective_sell_price(p_site_id, b.interval_start)
+              )::numeric,
+              4
+            ),
+            coalesce(b.actual_grid_power_w, 0)
+          )
         when b.plan_grid_w < -2000 and coalesce(b.actual_grid_power_w, 0) > 2500
           then format(
             'plán síť %s W vs skutečnost %s W (plán vývoz, skutečnost silný odběr)',
@@ -154,7 +177,7 @@ as $fn$
 $fn$;
 
 comment on function ems.fn_plan_actual_slot_guard_site(int, timestamptz) is
-'Poslední 2 uzavřené 15min sloty: fatální odchylka síť plán vs. audit → insert plan_fatal_deviation_sent (dedup); vrátí JSON s alerts k odeslání na Discord.';
+'Poslední 2 uzavřené 15min sloty: fatální odchylka síť plán vs. audit (včetně NEG_SELL_EXPORT při sell<0 a vývozu >4 kW) → insert plan_fatal_deviation_sent (dedup); JSON alerts pro Discord.';
 
 create or replace function ems.fn_plan_actual_slot_guard_all_active(
   p_now timestamptz default now()