Fix coloring of methods and add throughput lines in network vs runtime plots

[oruebel]

• The colors for different methods were chosen within each function, which led to inconsistent colors in particular when select methods were for some reason missing in a plot. This PR adds a fixed color palette to ensure consistent assignment of colors to methods across all plots.
• Add throughput (MB/s) lines to the plots showing the network traffic vs runtime

[Copilot]

Copilot review overview

🟡 Changes recommended

Fallback colors remain subset-dependent, and throughput guides misrepresent non-byte metrics.

Review effort: Balanced
Findings: 2

Open (2)

• Fallback colors vary with method order · New
• Throughput guides appear for non-byte metrics · New

What changed in this PR

Standardizes method colors across benchmark plots and adds throughput references to network-traffic-versus-runtime visualizations.

Changes:

• Adds a shared method palette across plot types.
• Adds dashed throughput guides, captions, and adjusted titles.

File	Description
src/​nwb_benchmarks/​database/​_visualization.py	Centralizes method colors and adds throughput overlays.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[CodyCBakerPhD]

One minor recommendation, either/or:

• Swap #9467BD for a color that also differs in brightness, for example a dark brown like #8C510A
• Tell zarr s3 and zarr s3 force no consolidated apart by marker or line style instead, since they're variants of the same method