[Feature] Configurable starting gold amounts in Homebrew settings

[TrezzeIohan]

Hi, guys! This is my first time contributing to a project; any feedback is appreciated.

This pull request aims to solve issue #734

Added initialAmount field to each currency type (coins, handfuls, bags, chests) in the Homebrew settings schema. Defaults match book values (0, 1, 0, 0).

• Homebrew.mjs: added initialAmount NumberField per currency; _initializeSource coerces empty submissions to 0; refreshConfig() syncs values to CONFIG.DH.RESOURCE.character.initialCurrency
• resourceConfig.mjs: added mutable initialCurrency object on character export
• actorField.mjs: added CharacterGoldField subclass that reads initial values from config at actor creation time
• character.mjs: switched from GoldField to CharacterGoldField
• settings.hbs: restructured currency section to CSS Grid with column headers ("Quantity Name" / "Starting Amount") instead of per-field inline labels
• settings.less: added .currency-rows grid styles
• en.json: added quantityName and initialAmount localisation keys

[CarlosFdez]

Hello, thank you for working on the PR.

The idea seems sound, though I have a few observations.

1. Disabled denominations will still get the initial value, which will be revealed when un-disabling it. The initial value should maybe set the values for disabled ones to zero somewhere.
2. Instead of making a CharacterGoldField subclass, you could add args to the GoldField to pass to the second parameter of the schemafield during initialization. You could then set an initial value callback from within the character itself.
3. Instead of outright giving up the schema based form input stuff (since formGroup doesn't work), you could use formInput instead. That should work for the text inputs.
4. Quantity Name doesn't feel like the right name for the column. Perhaps Denomination or Category Name? That's what its called in the book (both terms are used at various points on page 104 of the CRB).

[TrezzeIohan]

@CarlosFdez Thank you so much for your feedback!

I've addressed all the points you raised. Please feel free to leave any further comments.
Also, if this PR gets accepted, do you have any other issues you'd recommend I work on?

[Fix] Address PR review feedback for starting gold feature

• Disabled denominations now receive 0 at character creation
• Replace CharacterGoldField subclass with GoldField options callback;
  initial value logic now lives in character.mjs
• Use formInput instead of plain text inputs for denomination labels
• Rename "Quantity Name" column header to "Denomination"
• Remove initialCurrency from resourceConfig and currency sync from
  refreshConfig (no longer needed)