fix(ml): resolve all Julia module loading issues

- Reorder encoder.jl: PositionalEncoding and TransformerEncoderLayer
  defined before TextEncoder (fixes forward reference)
- Replace Transformers.jl dep (version conflicts) with local
  SimpleAttention implementation
- Rewrite server.jl from Oxygen.jl macros to plain HTTP.jl routing
  (Oxygen's @get/@post macros are incompatible with module includes)
- Fix BSON.@save/@load to use BSON.bson()/BSON.load() API
- Replace DataStructures LRU cache with simple Dict+Vector FIFO cache

Module loads successfully. Data loader reads JSONL. 18 provers registered.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

src/julia/EchidnaML.jl

@@ -29,7 +29,6 @@ using Zygote
 using CUDA
 using GraphNeuralNetworks
 using Graphs
-using Transformers
 using NNlib
 using Statistics
 using LinearAlgebra