feat: add trace_id to log output for OTel correlation

[DaleSeo]

Closes #686

Add trace_id=<32-hex> prefix to all log lines emitted within an OpenTelemetry-traced span, so operators can correlate logs with distributed traces. This is done via a custom FormatEvent wrapper that reads OtelData::trace_id() from the span chain before delegating to the default format.

• Before

❯ cargo run -p apollo-mcp-server -- ./examples/TheSpaceDevs/config.yaml
    Finished [`dev` profile [unoptimized + debuginfo]](https://doc.rust-lang.org/cargo/reference/profiles.html#default-profiles) target(s) in 11.38s
     Running `target/debug/apollo-mcp-server ./examples/TheSpaceDevs/config.yaml`
2026-04-15T14:40:55.330847Z  INFO Apollo MCP Server v1.12.0 // (c) Apollo Graph, Inc. // Licensed under MIT
2026-04-15T14:40:55.362467Z  INFO load_tool: Tool SearchUpcomingLaunches loaded with a character count of 545. Estimated tokens: 136
2026-04-15T14:40:55.368403Z  INFO load_tool: Tool ExploreCelestialBodies loaded with a character count of 761. Estimated tokens: 190
2026-04-15T14:40:55.373605Z  INFO load_tool: Tool GetAstronautDetails loaded with a character count of 898. Estimated tokens: 224
2026-04-15T14:40:55.378868Z  INFO load_tool: Tool GetAstronautsCurrentlyInSpace loaded with a character count of 501. Estimated tokens: 125
2026-04-15T14:40:55.395239Z  INFO schema_index: Indexed 50 types in 16.00ms
2026-04-15T14:40:55.398053Z  INFO Starting MCP server in Streamable HTTP mode port=8000 address=127.0.0.1

• After

❯ cargo run -p apollo-mcp-server -- ./examples/TheSpaceDevs/config.yaml
    Finished [`dev` profile [unoptimized + debuginfo]](https://doc.rust-lang.org/cargo/reference/profiles.html#default-profiles) target(s) in 0.60s
     Running `target/debug/apollo-mcp-server ./examples/TheSpaceDevs/config.yaml`
2026-04-15T14:36:32.060271Z  INFO Apollo MCP Server v1.12.0 // (c) Apollo Graph, Inc. // Licensed under MIT
trace_id=1b6ec242d9c61d3a49ae3d9a4abee507 2026-04-15T14:36:32.091848Z  INFO load_tool: Tool SearchUpcomingLaunches loaded with a character count of 545. Estimated tokens: 136
trace_id=50be2921f0ea177ceb4787b665e35369 2026-04-15T14:36:32.097931Z  INFO load_tool: Tool ExploreCelestialBodies loaded with a character count of 761. Estimated tokens: 190
trace_id=c9946787e06327ea3e883d6ffd33403e 2026-04-15T14:36:32.103155Z  INFO load_tool: Tool GetAstronautDetails loaded with a character count of 898. Estimated tokens: 224
trace_id=c293d31e37e814c80666dfc6515df595 2026-04-15T14:36:32.109268Z  INFO load_tool: Tool GetAstronautsCurrentlyInSpace loaded with a character count of 501. Estimated tokens: 125
trace_id=91e024fb2410f71cc8042bda55161cae 2026-04-15T14:36:32.126110Z  INFO schema_index: Indexed 50 types in 16.41ms
2026-04-15T14:36:32.128898Z  INFO Starting MCP server in Streamable HTTP mode port=8000 address=127.0.0.1

[apollo-librarian]

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[github-actions]

✅ Changeset file added - thank you!