ZBX-27897 - fix validation evidence
====================================

Server built from git tag 7.0.27 (./configure --enable-server --with-postgresql
--with-openssl --with-libevent --with-libcurl --with-libpcre2), run against a real
PostgreSQL backend. Temporary debug logging (LOG_LEVEL_WARNING, "ORPHANDBG ...") was
added at the two timer_revision=0 reset sites and at timer (re)creation
(dc_update_function_timer / dc_update_trigger_timer) to obtain ground truth. The
debug logging is NOT part of the submitted patch.

Method (deterministic, per-trial restart)
------------------------------------------
Each trial:
  1. restart the server (clean ZBX_DBSYNC_INIT -> the time-based timer is created once);
  2. disable the referenced item -> trigger becomes non-functional; within one timer
     period the timer pops while non-functional and timer_revision is reset to 0
     (logged: validate-reset / validate-reset-tr);
  3. re-enable the item (this is the next configuration-changing sync);
  4. check whether the timer is recreated afterwards (logged: upd-fn-timer / upd-tr-timer
     occurring after the reset line).

reset=1 confirms the orphan was actually induced in that trial (identical in both arms).
recreated=1 means the timer was rescheduled after re-enable -> trigger recovers.
recreated=0 means the timer stayed orphaned -> trigger frozen (the bug).

Restart-per-trial is used so every trial induces exactly one fresh orphan; the only
variable between the two arms is the server binary.

Test objects
------------
Function-timer path: item 900011 (trapper) + trigger 900101 = nodata(/host/900011,30s).
Trigger-timer path:  trigger 900102 = "time()>=0 and {900202}>=0", where {900202} =
                     last() on item 900011 (time() forces a trigger-level timer,
                     ZBX_TRIGGER_TIMER_TRIGGER; the item reference makes the trigger
                     non-functional when the item is disabled).

Results
-------
Function-timer path (nodata):
  VANILLA  trials 1..10: reset=1 recreated=0 => STUCK      (recovered=0  stuck=10)
  PATCHED  trials 1..10: reset=1 recreated=1 => RECOVERED  (recovered=10 stuck=0)

Trigger-timer path (time()):
  VANILLA  trials 1..10: reset=1 recreated=0 => STUCK      (recovered=0  stuck=10)
  PATCHED  trials 1..10: reset=1 recreated=1 => RECOVERED  (recovered=10 stuck=0)

Summary
-------
  vanilla 7.0.27 : 0/20 recovered  (20/20 stuck)   - reproduces the bug on both paths
  patched        : 20/20 recovered (0/20 stuck)    - timer recreated every time

In every one of the 40 trials the orphan reset was induced (reset=1), so the conditions
were identical across arms; vanilla never recreated the timer (trigger frozen), the
patched build recreated it every time (trigger resumes scheduled recalculation).

Single-step instrumented contrast (illustrative, function path)
---------------------------------------------------------------
  vanilla : upd-fn-timer (INIT) -> validate-reset (item disabled) -> [item enabled]
            -> NO upd-fn-timer  => trigger stays val=0 through a silent (no-data) probe
  patched : upd-fn-timer (INIT) -> validate-reset (item disabled) -> [item enabled]
            -> upd-fn-timer (drain re-fed the function) => trigger -> PROBLEM on the
               silent probe (timer alive again)

Build
-----
dbconfig.c / dbconfig.h compile with -Wall -Wextra and no new warnings; the patch
applies cleanly to the 7.0.27 tag.