DarkBlades Fabric 1.21.1 audit and multitool fix

Replace the previous DarkBlades JAR; install Fabric API and use Java 21 or newer.

The attached 1.21.1 recipe contained a Dark Ingot instead of the fourth tool.
The source reference also had the three-tool recipe; this was not a Minecraft limit.
Recipe now matches the supplied screenshot: top pickaxe, left hoe, center catalyst,
right axe, bottom shovel. Sword behavior is included without a sword ingredient.

Multitool: pickaxe/axe/shovel/hoe mining, cobweb cutting and sword sweep attacks.
Right-click strips logs, scrapes copper, removes wax, makes paths or douses campfires.
Sneak-right-click prioritizes tilling soil. Uses vanilla tool interaction logic.
Added shovel/hoe tags and full tooltip. Respects netherite incorrect-block tag.
Mining/hitting costs one durability; maximum durability 8000, damage 20,
attack speed 1.8, mining speed 13 on the four mineable block categories.

Removed ignored legacy plural tag paths and obsolete Forge mining-level tags.
Restored cluster_max_harvestables to the valid singular item-tag path.
Added explicit empty hammer repair tag (original hammer has no repair ingredients).
Fixed staff break animation/equipment slot when fired from offhand.

115 live server checks passed on Minecraft 1.21.1 / Fabric Loader 0.19.5 /
Fabric API 0.116.17+1.21.1. Java 21 bytecode; test server ran Java 25.
Tests included all 35 crafting recipes and catalyst smelting (15s, 1 XP),
hammer crafting remainder with name/enchantments retained and one durability used,
last-durability hammer break, tool/enchantment tags, tool speeds and repairs,
normal ore drops (2 dust), Silk Touch (1 ore), dark block drops and harvest tiers,
right-click actions in both hands, actual sweep damage and tool durability.
Ore feature was present in 53 Overworld biomes, absent from tested Nether biome,
and generated actual ore blocks. Settings retained: 8 attempts/chunk,
vein size 10, Y -64..64. No recipe or mod tag loading errors.
All 112 JSON files parsed; referenced mod item textures and item tags resolved.
Armor stats and texture paths checked against source. Client rendering and
physical input were not tested, nor was every possible mod interaction.

Source project and test harness are included in META-INF/darkblades-source.zip.
The source can be built with Gradle 8.11.1 / Java 21 using Fabric Loom.
No test-only mod classes are included in the runnable mod.
