feat(curve, waveform): add dap_parameters for lmfit customization in DAP requests

[wyzula-jan]

Description

Extend the Waveform widget DAP integration to allow passing lmfit parameter overrides/fixed values from the GUI/API into the backend fit service. Waveform.plot() and Waveform.add_dap_curve() now accept dap_parameters (dict or lmfit.Parameters) which are serialized into the DAP request and applied server-side for any lmfit model (including SineModel). The server now merges partial overrides with model.make_params() so users can provide only a subset of parameters without triggering “Missing parameters” errors. Added server-side logging to make configuration and fit failures easier to debug, and expanded the Waveform demo launch script with examples of all supported parameter formats.

Has to be reviewed together with bec-project/bec#707

Type of Change

• Add dap_parameters passthrough and storage on DAP curves (Waveform.plot/add_dap_curve → DAP
  request).
• Generalize backend parameter handling to accept partial overrides for all lmfit models (merge with
  defaults, filter unknown names) and improve fit/config logging.
• Multiple LMFitModels can be used for one DAP curve

How to test

• Launch the Waveform demo (bec_widgets/bec_widgets/widgets/plots/waveform/waveform.py) and verify:
• Gaussian fits work with no params, easy dict ({"amplitude": 1.0}), lmfit-style dict, and
  lmfit.Parameters.
• Try to use the rpc to set dap_params

[Copilot]

Pull request overview

This PR adds support for customizing lmfit parameters in DAP (Data Analysis Pipeline) requests, allowing users to override default fitting parameters when creating DAP curves for waveform plots.

Key changes:

• Added dap_parameters parameter to plot() and add_dap_curve() methods, accepting dict or lmfit.Parameters
• Implemented _normalize_dap_parameters() method to serialize various parameter formats for the DAP server
• Modified request_dap() to include normalized parameters in DAP request messages
• Extended DeviceSignal model to store dap_parameters

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
bec_widgets/widgets/plots/waveform/waveform.py	Added dap_parameters support throughout the waveform plotting API, including parameter normalization logic and updated DAP request handling. Includes demo examples showing different parameter input formats.
bec_widgets/widgets/plots/waveform/curve.py	Extended DeviceSignal model with optional dap_parameters field to store serialized parameters.

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[codecov]

Codecov Report

❌ Patch coverage is 62.76596% with 35 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
bec_widgets/widgets/plots/waveform/waveform.py	61.95%	21 Missing and 14 partials ⚠️

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