Add resistor/capacitor/SMD value calculator with component image generation

[Sebbeben]

Component value calculator & image generator

Adds a Value calculator tool (Tools menu) that decodes/encodes the value of common components and generates a clean SVG picture you can attach to a part — handy for assortments (e.g. AliExpress kits) imported with blank thumbnails and sparse data.

Calculator tabs

Each tab is a bidirectional decoder/encoder, draws the part to the selected package with a collapsible "appearance" panel, and can attach the rendered image (optionally as the master picture):

• Resistor — 4/5/6-band colour code
• Capacitor — value ↔ 3-digit code ↔ tolerance
• SMD resistor — value ↔ 3-digit / 4-digit / EIA-96 code
• Inductor — colour-band code
• SMD inductor — value ↔ µH code

Bulk "Generate component images" (parts-table action)

• Classifies each selected part (resistor / capacitor / inductor / diode / LED, THT or SMD) with ComponentValueGuesser and detects value, voltage, tolerance, power, ppm, pitch, diameter, colour, SMD package and marking from the name, description and parameters.
• Renders a preview per part, lets you tweak appearance, and attaches the images in one go.
• Can also write matching KiCad symbol/footprint/reference-prefix EDA fields for the whole selection.

Implementation

• ComponentValueGuesser — classification + detection + EDA suggestion.
• GeneratedImageAttachmentHelper — stores the SVG through the existing attachment pipeline, so every generated image is run through the SVG sanitizer on save.
• Two POST endpoints on PartController (generate_image, set_eda) guarded by edit + CSRF.
• New @tools.value_calculator permission, a Tools-tree entry, and docs.
• All drawing is client-side in a Stimulus controller; the un-sanitized live preview escapes part-derived text and validates colours as defence-in-depth.

Tests

Unit tests for ComponentValueGuesser and functional tests for the endpoints, including permission/CSRF enforcement and the persisted side effects.

Open question for review

The tool is currently called a "calculator", but roughly half its value is image generation for real parts, and some tabs are really decoders/converters. Happy to rename or restructure (e.g. "Component value & image tool", or split "Decoder" vs "Image generator") — whatever fits Part-DB best.

Screenshots to follow.

[codecov]

Codecov Report

❌ Patch coverage is 85.96803% with 79 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.11%. Comparing base (12b53f1) to head (0ec45ac).
⚠️ Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
src/Services/Tools/ComponentValueGuesser.php	90.55%	34 Missing ⚠️
src/Controller/ToolsController.php	84.00%	16 Missing ⚠️
...ces/Attachments/GeneratedImageAttachmentHelper.php	70.45%	13 Missing ⚠️
src/Controller/PartController.php	78.26%	10 Missing ⚠️
src/Services/Parts/PartsTableActionHandler.php	14.28%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #1435      +/-   ##
============================================
+ Coverage     58.50%   59.11%   +0.61%     
- Complexity     8713     8946     +233     
============================================
  Files           640      642       +2     
  Lines         28197    28762     +565     
============================================
+ Hits          16496    17003     +507     
- Misses        11701    11759      +58     

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