prepare release 1.15 (#2707)

* bump version
* fix invisible class on labels
* fail safe removal of foreign key
* check if optional form field exists before accessing it
* silently ignore stopped timesheets
* prevent colliding parameter names
* make sure decimal duration is always rendered with two decimals
* simplify translation
* fix #2751 ANSI_QUOTES
* rename composer task
* fix billable statistic rates
* added missing translation for export

composer.json

@@ -146,7 +146,7 @@
         "kimai:pre-commit":  [
             "@kimai:codestyle",
             "@kimai:phpstan",
-            "@kimai:code-lint",
+            "@linting",
             "@kimai:tests-unit"
         ],
         "kimai:code-check": "@code-check",
@@ -154,7 +154,8 @@
             "@kimai:pre-commit",
             "@kimai:tests-integration"
         ],
-        "kimai:code-lint":  [
+        "kimai:code-lint": "@linting",
+        "linting": [
             "composer validate --strict",
             "bin/console lint:container",
             "bin/console lint:yaml config --parse-tags",