[MINOR] Simplify build creation and set selection presentation

[RyanS4]

Summary

Refine build creation and its nested set picker into a coherent, readable form using the existing fields and workflow. The current form relies on small uppercase text, many nested outlines, duplicated headings, and hardcoded catalog counts that make an already detailed editor unnecessarily difficult to scan.

Current Behavior

• BuildCreatorModal.jsx L:247-363 repeats "Custom Loadout" and "Create Custom Build", uses decorative uppercase form labels, and claims there are "all 712 ESO sets" in static helper copy.
• L:365-502 presents thirteen equipment editors containing slot, weight, item, set, Change Set, weight/type controls, trait, enchantment, tradeability, and source information in densely bordered boxes. Essential labels reach 9-10px and source names are truncated.
• L:524-577 opens a nested picker with another count/title stack, a second hardcoded "712" claim, and a dense horizontal category strip.
• L:579-641 compresses set metadata and bonus previews inside further boxes, then says "Click a set to equip" even though the action changes the planned build.
• L:187-219 and L:275-294 use long authentication/error wording that distracts from the specific next action.

Target Architecture / Expected Behavior

Apply #104's form, typography, spacing, and dialog foundations to the existing editor.

1. Use the single title Create build. Arrange the currently rendered title, class, role, and notes fields as a straightforward form, with clear labels and readable entered values.
2. Use Build name, Notes and rotation, Equipment, and Enchantment. Replace the static catalog claim with Choose a set, item type, trait, and enchantment for each slot.
3. Give each equipment editor a clear order: slot and item identity, current set and Change set action, weight/weapon type, then trait and enchantment. Keep the current values, allowed choices, restrictions, source, and tradeability visible.
4. Reduce repeated borders and redundant decorative weight badges when the same value is already visible in its current control. Preserve information about a restricted single weight; do not change allowed options or the resolution behavior.
5. Ensure text inputs, selects, weight buttons, and Change set use consistent typography and heights. Keep the existing Cancel, Save build, saving, and disabled states in the current workflow.
6. Nested picker title: Choose a set for {slot}. Show its existing dynamic count as secondary text. Search placeholder: Search sets by name, bonus, or source. Keep every category filter and existing selection behavior.
7. Present set name first, source/category/weights second, and existing bonus preview third. Give long metadata room to wrap; avoid tiny text inside a second heavy frame.
8. Replace Click a set to equip with Select a set for this slot. Shorten authentication guidance to Sign in to save this build and missing-title validation to Enter a build name.

Preserve all currently rendered fields, defaults, thirteen slot editors, option lists, weight restrictions, set resolution, payload fields, validation conditions, authentication rules, save/cancel flow, and nested picker behavior. This issue adds no wizard, presets, new editor steps, new author/source fields, or in-game equipment actions.

Files Affected

• frontend/src/components/builds/BuildCreatorModal.jsx (L:187-219, L:247-649)
• Shared form/dialog styles and primitives established by [FEAT] Establish Tailwind v4 design tokens and incrementally migrate core UI #104, consumed consistently.

Severity & Acceptance Criteria

Severity: MINOR. Priority: Tier 3 - UI & User Experience. The changes improve readability and wording within the existing creation workflow.

• The form has one clear title and readable labels; essential controls no longer depend on the current 9-10px uppercase text.
• Every existing field, slot, choice, restriction, source, tradeability value, and action remains available.
• Selected weight, weapon type, trait, and enchantment are immediately distinguishable from labels and other choices.
• Long item/set/source names do not overlap Change set or become inaccessible through layout clipping.
• Static "712 sets" claims are removed from application helper text; the existing dynamic catalog/result count remains accurate to current data.
• At 360px and 390px widths, short viewport heights, and 200% zoom, both dialogs remain contained and scrollable with existing close/cancel/save controls reachable.
• Review screenshots for armor, jewelry, weapon, restricted weight, category selection, long set metadata, empty search, loading sets, saving, authentication, and validation presentations.
• Existing defaults, field updates, set filtering/resolution, payloads, save callbacks, and close behavior remain unchanged. Relevant existing frontend checks pass with zero errors.

Dependencies & Blockers

• Blocked By: [FEAT] Establish Tailwind v4 design tokens and incrementally migrate core UI #104
• Prerequisite For: None