Handle "would clobber existing tag" during --refresh

[vsc55]

Problem

Running ./freepbx_git.php --refresh aborted on any repo whose remote had a moved or recreated tag. git fetch --tags fails in that case with would clobber existing tag and returns a non-zero status, which bubbled up as an uncaught, empty exception:

PHP Fatal error:  Uncaught Exception in /usr/src/devtools/libraries/Git.php:262
Stack trace:
#0 Git.php(277): GitRepo->run_command()
#1 Git.php(728): GitRepo->run()
#2 freepbx.php(139): GitRepo->fetch()
#3 freepbx_git.php(237): freepbx::refreshRepo()

The message was empty because the -q flag suppressed the stderr that would have explained the failure, and a single bad repo aborted the entire refresh run.

Changes

• Git::fetch($force = false) — optional flag that adds --force to the tag fetch. The library stays non-interactive.
• freepbx::refreshRepo(..., $force = false) — wraps the fetch in a try/catch. On failure it forces the tag update when $force is set, otherwise prompts for that repo. Declining now reports a clear error and continues with the next module instead of crashing the whole run.
• freepbx_git.php --refresh — resolves the force mode from --force (or -y), or asks once upfront whether to force automatically or be prompted on each conflict. --refreshhard forces tags automatically.
• Documented the --force flag in the help output.

Behavior

Command	On tag conflict
--refresh	Asks once upfront: force always, or prompt per repo
--refresh --force	Forces tag updates, no prompts
--refresh -y	Same as --force
--refreshhard	Forces tag updates automatically