PotionCombine

• now targets paper 1.21+, 1.20.x support dropped. setBasePotionData went with it — results use setBasePotionType, which closes the oldest TODO in the codebase
• old PotionType spellings in recipes.yml (INSTANT_HEAL, REGEN, JUMP, SPEED) still work, they map onto the renamed enum
• builds with java 21 now, gradle fetches one itself if the machine doesn't have it
• /pc journal: the "•" line marker rendered as mojibake — the build had lost its utf-8 source encoding, so the bullet literal was read in the platform charset. put the encoding back, it renders again

⚠ heads up: 1.4 drops 1.20.x. still on 1.20? stay on 1.3.1.