feat(export): enhance ODCS HTML export

[GauthierCapouillez]

Summary

The current ODCS HTML export is generated from a single monolithic Jinja2 template
(datacontract_odcs.html, ~688 lines). This PR introduces a complete overhaul:
the template is decomposed into focused, reusable partials and macros, the layout
is modernised to match the visual design of the datacontract-editor React app, and
semantic HTML markup issues are fixed.

Motivation

• The monolithic template is hard to maintain, extend, and test.
• HTML display fits to datacontract-editor display rules
• Invalid <dt>/<dd> elements used outside a <dl> parent caused browsers to
  silently repair the DOM, breaking CSS space-y-* selectors and producing
  inconsistent vertical spacing between sections.

Changes

Architecture — Modular partials

datacontract_odcs.html is reduced to ~45 lines (assembler only).
All rendering logic is extracted into partials_odcs/:

Partial	Renders
header.html	Top navigation bar
title.html	Contract title, status badges, YAML dialog trigger
fundamentals.html	Core metadata (name, version, ID, owner, tags…)
term_of_use.html	Description — purpose, usage, limitations
diagram.html	Entity-relationship Mermaid diagram
schema.html	Schema tables with nested properties
servers.html	Server list with per-type icons
team.html	Team contact card
support.html	Support channels
roles.html	Access roles
pricing.html	Pricing information
sla.html	SLA properties
custom_properties.html	Custom properties (mapping or list formats)
dialog_yaml.html	Full YAML modal dialog
footer.html	Footer

Architecture — Reusable macros

• macros/schema.html — recursive render_nested_properties with type tooltips, badges
• macros/server.html — server_icon mapping 30+ server types to SVG icons
• macros/support.html — support channel icon/link rendering
• macros/authoritative_definitions.html — authoritative definition badges

Visual design

• Card-based layout consistent with datacontract-editor
• Consistent space-y-6 vertical rhythm between all sections
• Responsive grids for properties
• Colour-coded status badges (Draft, Active, Deprecated, …)
• Server type icons (BigQuery, Databricks, Snowflake, Kafka, PostgreSQL, …)
• Support channel icons (Slack, email, GitHub Issues, Jira, …)
• Panzoom-enabled ERD diagram + YAML source modal

Bug fixes

• Semantic markup: <dt>/<dd> outside <dl> replaced with <div> in
  team, term_of_use, roles, sla, servers — invalid usage caused silent
  browser DOM repair breaking space-y-* selectors.
• Custom properties: migrated from <table> to <dl>/grid; supports both
  mapping and list input formats; break-all prevents horizontal overflow.

Testing

uv run pytest tests/ -k "html or export" → 129/129 pass.
Full suite (no Docker): 1080 pass, 0 regressions.

• Tests pass (uv run pytest)
• Code formatted (uv run ruff check --fix && uv run ruff format)
• Docs updated (if relevant)
• CHANGELOG.md entry added

[GauthierCapouillez]

@simonharrer As requeted, I updated the html export to fit to datacontract-editor visualization