Fix X3DH + add web client served by warzone-server

X3DH fix:
- Added identity_encryption_key (X25519) to PreKeyBundle
- initiate() and respond() now use correct DH operations per Signal spec:
  DH1=IK_a*SPK_b, DH2=EK_a*IK_b, DH3=EK_a*SPK_b, DH4=EK_a*OPK_b
- All 17 tests pass including x3dh_shared_secret_matches

Web client (served at /):
- Identity generation with seed (stored in localStorage)
- Recovery from hex-encoded seed
- Auto-load saved identity on page load
- Fingerprint display (same format as CLI: xxxx:xxxx:xxxx:xxxx)
- Key registration with server via /v1/keys/register
- Chat UI with message polling (5s interval)
- Commands: /help, /info, /seed
- Dark theme matching warzone aesthetic

Both clients (CLI + Web) now exist:
- CLI: warzone init, warzone info, warzone recover
- Web: http://localhost:7700/ (served by warzone-server)

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

warzone/target/debug/build/libc-26e3aa07cdcb9961/invoked.timestamp

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+This file has an mtime of when this was started.

warzone/target/debug/build/libc-26e3aa07cdcb9961/output

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+cargo:rerun-if-changed=build.rs
+cargo:rerun-if-env-changed=RUST_LIBC_UNSTABLE_FREEBSD_VERSION
+cargo:rustc-cfg=freebsd12
+cargo:rerun-if-env-changed=RUST_LIBC_UNSTABLE_MUSL_V1_2_3
+cargo:rerun-if-env-changed=RUST_LIBC_UNSTABLE_LINUX_TIME_BITS64
+cargo:rerun-if-env-changed=RUST_LIBC_UNSTABLE_GNU_FILE_OFFSET_BITS
+cargo:rerun-if-env-changed=RUST_LIBC_UNSTABLE_GNU_TIME_BITS
+cargo:rustc-check-cfg=cfg(emscripten_old_stat_abi)
+cargo:rustc-check-cfg=cfg(espidf_time32)
+cargo:rustc-check-cfg=cfg(freebsd10)
+cargo:rustc-check-cfg=cfg(freebsd11)
+cargo:rustc-check-cfg=cfg(freebsd12)
+cargo:rustc-check-cfg=cfg(freebsd13)
+cargo:rustc-check-cfg=cfg(freebsd14)
+cargo:rustc-check-cfg=cfg(freebsd15)
+cargo:rustc-check-cfg=cfg(gnu_file_offset_bits64)
+cargo:rustc-check-cfg=cfg(gnu_time_bits64)
+cargo:rustc-check-cfg=cfg(libc_deny_warnings)
+cargo:rustc-check-cfg=cfg(linux_time_bits64)
+cargo:rustc-check-cfg=cfg(musl_v1_2_3)
+cargo:rustc-check-cfg=cfg(musl32_time64)
+cargo:rustc-check-cfg=cfg(vxworks_lt_25_09)
+cargo:rustc-check-cfg=cfg(target_os,values("switch","aix","ohos","hurd","rtems","visionos","nuttx","cygwin","qurt"))
+cargo:rustc-check-cfg=cfg(target_env,values("illumos","wasi","aix","ohos","nto71_iosock","nto80"))
+cargo:rustc-check-cfg=cfg(target_arch,values("loongarch64","mips32r6","mips64r6","csky"))

warzone/target/debug/build/libc-26e3aa07cdcb9961/root-output

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+/Users/manwe/CascadeProjects/arvan/warzone/target/debug/build/libc-26e3aa07cdcb9961/out