chore(infra): Phase 4a — batch Rust low-risk minors + MSRV bump to 1.95

[Detair]

Summary

Phase 4a of the dep-update sweep (spec, plan). Builds on Phase 3 (#551).

Workspace deps

• axum-tracing-opentelemetry 0.32 → 0.33
• init-tracing-opentelemetry 0.36 → 0.37
• infer 0.16 → 0.19 (signature DB updated; tests build)
• smol_str 0.2 → 0.3 (server compiles cleanly; no From<&str> migration needed)
• tokio-tungstenite 0.28 → 0.29 (server compiles cleanly; no MaybeTlsStream exhaustiveness fixes needed)

Client deps

• sentry, sentry-tracing 0.47 → 0.48. The tower integration moved out of the sentry crate in 0.48; we use sentry-tracing (not the tower middleware), so no migration.
• sysinfo 0.38 → 0.39 — requires Rust 1.95, so this PR also bumps MSRV.

Workspace hygiene

• tempfile = "3" hoisted to [workspace.dependencies]. server/Cargo.toml and client/src-tauri/Cargo.toml (dev-deps) now use tempfile.workspace = true.
• client/src-tauri/vp8-decoder/Cargo.toml: thiserror = "1" → thiserror.workspace = true (= 2). vp8-decoder now aligns with the workspace's thiserror major.

MSRV bump 1.93 → 1.95

sysinfo 0.39 declares rust-version = "1.95". CI uses dtolnay/rust-toolchain@stable and stable rust is currently 1.95.0 (released 2026-04-14), so CI is unaffected. Local development requires rustup update stable.

Side effects of the rustc 1.95 toolchain bump (rustc 1.95 introduced new clippy lints that fire on existing code):

• websocket_integration.rs ×3: Duration::from_millis(1000) → Duration::from_secs(1) (clippy::duration_suboptimal_units)
• media_processing.rs ×1: inline format arg "…{error}" instead of positional (clippy::uninlined_format_args)
• observability.rs ×2: switched let req: i64 = 100; …let err: i64 = 5; … err as f64 / req as f64 … to native f64 literals in the test helper (clippy::needless_type_cast)

These are mechanical fixes only — no behavioural change.

Tauri 2.11 schema regeneration (carry-over from #551)

client/src-tauri/gen/schemas/{acl-manifests,desktop-schema,linux-schema}.json are auto-regenerated by tauri-build from the 2.11 ACL set. Phase 3 (#551) only ran bun run build locally (no Rust client compile, libspa local-env issue), so the schema regeneration didn't get committed there. Phase 4a's local Rust check triggered the regen; including the diff here so the on-disk schemas match the committed Tauri version. Pure data movement, no manual edits.

Test plan

• cargo fmt --check — clean
• cargo clippy --tests -p vc-server -- -D warnings — clean
• cargo deny check — advisories ok, bans ok, licenses ok, sources ok
• cargo audit — exit 0 (warning count 26 → 25; one transitive cleared)
• cargo build --tests -p vc-server — clean
• cargo check -p vc-common -p vc-crypto -p kaiku-vp8-decoder — clean
• bun run test:run — 32 files, 581/581 tests pass
• bun run build — tsc && vite build green
• cargo build --release -p vc-client — deferred to CI; pre-existing local libspa env issue prevents full Rust client builds locally

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