Feature - Add support for a fiscal year period defined in user settings.

* Add "This fiscal year", "Last fiscal year" as date range options in Transaction Details to filter transactions to those periods
* Add fiscal year ranges to Statistics & Trend Analysis
* Add "fiscal year start date" to user profile settings, allowing the user to select any date of the calendar year as the start of the fiscal year
* Add "fiscal year format" to user profile settings, allowing the user to specify how financial year date labels should appear

Implementation notes:
* The default fiscal year start is January 1 and the default fiscal year display format is "FY 2025"
* Fiscal year start date (month number & day number) are stored together in db as a uint16, high byte & low byte respectively
* February 29 is disallowed as a fiscal year start date, since it is never used as a convention in any country
* Jest is added to the project as a dev dependency, for unit tests in frontend

Signed-off-by: Sebastian Reategui <seb.reategui@gmail.com>

cmd/webserver.go

@@ -98,6 +98,7 @@ func startWebServer(c *core.CliContext) error {
 		_ = v.RegisterValidation("validCurrency", validators.ValidCurrency)
 		_ = v.RegisterValidation("validHexRGBColor", validators.ValidHexRGBColor)
 		_ = v.RegisterValidation("validAmountFilter", validators.ValidAmountFilter)
+		_ = v.RegisterValidation("validFiscalYearStart", validators.ValidateFiscalYearStart)
 	}
 
 	router.NoRoute(bindApi(api.Default.ApiNotFound))