fix: wire up remote thesaurus loading and remove memoize overhead

[AlexMikhalev]

Summary

• Wire up the existing read_url function in load_thesaurus so AutomataPath::Remote actually fetches from the URL instead of returning an error (was dead code)
• Remove #[memoize] from magic_pair/magic_unpair -- trivial u64 arithmetic where hash-table lookup overhead exceeds computation cost
• Replace with #[inline] for proper optimization
• Remove memoize crate dependency from terraphim_rolegraph

Impact

• Remote thesaurus loading now works end-to-end with remote-loading feature
• Hot-path pairing operations are faster without hash-table overhead
• One fewer dependency in rolegraph (removes memoize + its proc-macro crate)

Fixes #138, Fixes #143

Test plan

• cargo test -p terraphim_automata -- 83 passed (45 unit + 30 integration + 7 paragraph + 5 doc - 4 overlap)
• cargo test -p terraphim_rolegraph -- 34 passed (20 unit + 14 proptest)
• cargo test -p terraphim_middleware -p terraphim_service -- 52 suites, 0 failures
• cargo clippy -- clean
• cargo fmt -- clean

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