port to Minecraft 26.3

Source changes for 26.3 API breakage:
- block codec system removed upstream (Block has no MapCodec/codec()/
  simpleCodec anymore): drop CODEC + codec() from AmethystCauldronBlock
  and GravityCrystalBlock
- Entity.hurtMarked -> Entity.syncVelocity (pure rename, still public)
- LivingEntity.drop() now takes a Prediction; our drops are server-
  initiated and unpredicted, so they pass SERVER_ONLY
- canSimulateMovement() became final; the ravager/hoglin mount mixins
  now override getMoveSimulationType() and return
  AUTHORITATIVE_SIDE_AND_SERVER, which is the same "server always
  simulates" semantics the old !isClientSide branch had
- loot number providers split into providers.number.{ints,floats} and
  became Holder-based: UniformGenerator.between(1f,3f) ->
  ContextIntProviders.between(1,3)
- BonemealableBlock methods take a BonemealSource (INTERACTION here)
- clockManager().getTotalTicks(c) ->
  clockManager().getInstance(c).totalTicks()
- EnderMan -> Enderman (capitalisation only)

Build: MC 26.3, loader 0.19.5, fabric-api 0.160.5+26.3, loom 1.18.1,
gradle wrapper 9.6.0 -> 9.7.1 (loom 1.18.x requires Gradle >= 9.7).
Polymer is 0.18.0+26.3-rc-1: upstream has not published a 26.3-final
build yet, that rc build is the only one on the 26.3 line.

server-deploy: pack.toml -> 26.3 / loader 0.19.5; fabric-api, polymer
and simple-voice-chat are the only pack mods with 26.3 builds and were
updated (index hashes regenerated). The remaining third-party mods have
no 26.3 release yet and are deliberately left untouched. Dockerfile now
pins the justbackup and fabric-carpet forks to their 26.3 branches
instead of silently building whatever the default branch holds.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

server-deploy/pack/pack.toml

@@ -6,11 +6,11 @@ pack-format = "packwiz:1.1.0"
 [index]
 file = "index.toml"
 hash-format = "sha256"
-hash = "d7c215cba51d8e9324316d5c236c6f03727012917340b2100c868614170ba69e"
+hash = "7524eced8051fa2ae3e84ae584afcf9863dd121db99555618b517447540daed1"
 
 [versions]
-fabric = "0.19.3"
-minecraft = "26.2"
+fabric = "0.19.5"
+minecraft = "26.3"
 
 [options]
-acceptable-game-versions = ["26.1", "26.1.2"]
+acceptable-game-versions = ["26.2"]