chore: extract shared factory for notification diagram configs

[elfensky]

Source: desloppify review (abstraction_fitness)

Problem

Three diagram config files (inAppFlowConfig.js, notificationFlowConfig.js, pushFlowConfig.js in src/app/docs/notifications/) repeat the same {views, flows, legend, title, description, details} shape with no shared schema or factory. Adding a new field requires editing all three files.

Similarly, three definition files (*Definition.js) repeat identical DEFINITION_LR = 'graph LR\n' + BODY / DEFINITION_TD export patterns.

Fix

1. Extract a createFlowConfig(options) factory or a @typedef for the config shape
2. Extract a buildMermaidDefinition(body) helper for the LR/TD assembly

Files

• src/app/docs/notifications/inAppFlowConfig.js
• src/app/docs/notifications/notificationFlowConfig.js
• src/app/docs/notifications/pushFlowConfig.js
• src/app/docs/notifications/inAppFlowDefinition.js
• src/app/docs/notifications/notificationFlowDefinition.js
• src/app/docs/notifications/pushFlowDefinition.js

Impact

Low — docs-only code, no runtime effect. Reduces maintenance surface for diagram additions.