Fix variables form dialog resize glitch for templates with many variables

[PriyankaaXD]

Closes #59

Problem

As reported by @amandamcg in the discussion on #59, the fix in 0aa28b4 (max-height + overflow scroll on .variablesForm) didn't fully solve the issue — the dialog would open short, grow, then slowly contract, instead of opening at a stable size. This happens because the dialog was left at Joplin's default setFitToContent: true, so the core app auto-resizes the iframe to content height dynamically, which races against the plugin's own CSS max-height constraint.

Fix

Explicitly call joplin.views.dialogs.setFitToContent(this.dialog, ...) on every dialog open, based on the current template's variable count — true (compact, auto-sized) for 5 or fewer variables, false (fixed 90vw x 80vh, scrollable) for more than 5.

Note: this must be set explicitly every time, not only conditionally disabled, because the dialog handle (dialogViewHandle) is created once in index.ts and reused across every template use. An earlier version of this fix only called setFitToContent(false) when variable count was high, which caused the false state to leak into the next dialog use even when that template had few variables. Setting it explicitly on every open avoids this.

Testing

Tested manually on Windows, across multiple orderings in the same session:

• Template with 3 variables (text fields) — dialog opens compact/auto-sized.
• Template with 18 variables (mix of text, dropdown, date, number, time, boolean) — dialog opens at a stable size immediately, no grow/shrink glitch, all fields reachable via scroll.
• Confirmed both cases work correctly regardless of which was opened first in the session (this was the actual bug in an earlier version of this fix).

Screenshots below show both cases.

[ test2 - 3 variables, compact dialog]
[Test Template - Many Vars - 18 variables, stable scrollable dialog]

[PriyankaaXD]

Happy to make any changes if you'd like a different threshold or approach.