fix(fusion_clock): settings audit — remove 2 dead knobs, make IP-fallback + all Boolean toggles work

Audit of all 41 settings found 3 that were shown but read nowhere, and 17 Boolean
toggles that couldn't be turned OFF.

- Remove grace_period_minutes (orphaned by the schedule-driven cron rewrite) and
  weekly_overtime_threshold (never implemented): field + view + seed.
- enable_ip_fallback now actually gates _verify_location's IP-whitelist check
  (default ON to preserve current behaviour).
- All 17 fusion_clock Boolean settings now persist explicitly as 'True'/'False'
  via a _FCLK_BOOL_PARAMS loop in get_values/set_values (config_parameter Booleans
  can't store False, so OFF never stuck). Add round-trip tests. Bump 3.15.2 -> 3.16.0.

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

fusion_clock/views/res_config_settings_views.xml

@@ -52,10 +52,6 @@
                             <field name="fclk_enable_auto_clockout"/>
                             <div class="content-group" invisible="not fclk_enable_auto_clockout">
                                 <div class="row mt16">
-                                    <label for="fclk_grace_period_minutes" string="Grace (min)" class="col-lg-5 o_light_label"/>
-                                    <field name="fclk_grace_period_minutes"/>
-                                </div>
-                                <div class="row mt8">
                                     <label for="fclk_max_shift_hours" string="Max Shift" class="col-lg-5 o_light_label"/>
                                     <field name="fclk_max_shift_hours" widget="float_time"/>
                                 </div>
@@ -83,10 +79,6 @@
                                     <label for="fclk_daily_overtime_threshold" string="Daily Limit" class="col-lg-5 o_light_label"/>
                                     <field name="fclk_daily_overtime_threshold" widget="float_time"/>
                                 </div>
-                                <div class="row mt8">
-                                    <label for="fclk_weekly_overtime_threshold" string="Weekly Limit" class="col-lg-5 o_light_label"/>
-                                    <field name="fclk_weekly_overtime_threshold" widget="float_time"/>
-                                </div>
                             </div>
                         </setting>
                     </block>