style: lint and format src/djehuty/web/ui.py with ruff, enforce

[641e16]

Note: Stacked on #173 - only the last two commits are new here;
I'll rebase onto main once #173 merges.

Summary

Next slice of the incremental Ruff rollout (#66): lints and formats src/djehuty/web/ui.py and adds it to the enforced scope. Split into a mechanical commit (pure ruff check --fix + ruff format output, safe to skim) and a manual commit (the changes that required judgment, worth review).

Changes

• src/djehuty/web/ui.py (commit 1, mechanical): apply ruff check --fix and ruff format. No functional changes; all 23 long-line
  violations were resolved by the formatter.
• src/djehuty/web/ui.py (commit 2, manual): swap the # pylint: disable=unused-import comments for # noqa: F401 on the five optional-dependency availability probes (SAML, pyvips, uwsgi, boto3); rename three module-local exceptions to carry the Error suffix (N818); fix one incorrect docstring (see Notes).
• justfile: add the file to lint_paths so just lint and CI enforce it.

Approval Checklist

• I agree to follow Djehuty's code of conduct.
• I have read and I have follow the code contribution workflow.
• Code style and conventions were respected.
• Documentation has been updated where needed (README, docs, or examples).
• Review approved by at least one maintainer.
• Merge readiness (PR is squashed into a single commit and follows the commit template).

Issue Reference

Closes #147 (part of #66)

Screenshots (optional)

Green CI run on my fork with the Lint job covering the extended scope:
https://github.com/641e16/djehuty/actions/runs/29643501215

Notes (optional)

• !!! Three exception renames, verified contained: ConfigFileNotFound -> ConfigFileNotFoundError, UnsupportedSAMLProtocol -> UnsupportedSAMLProtocolError,
  DependencyNotAvailable -> DependencyNotAvailableError.
• All three are defined, raised, and caught inside ui.py (verified by grep), so nothing outside this file is affected.
• The five "unused" imports are deliberate availability probes (try/except import setting *_DEPENDENCY_LOADED flags). Ruff correctly refuses to auto-remove them; the pylint suppression comments were replaced with # noqa: F401 -- availability probe, since Ruff supersedes pylint now.
• While renaming, I found ConfigFileNotFoundError's docstring claimed it was about the database being unqueryable ; probably a copy-paste artifact?? It now describes what the code does: the exception fires when a file parses but is not a Djehuty configuration file (actual missing files raise the builtin FileNotFoundError). The name is therefore still slightly misleading -> InvalidConfigurationFileError would be more truthful i think but a rename felt out of scope for a formatting PR. I can still do it here or in a follow-up if preferred.
• Verified: just lint green on the full scope; module imports cleanly; unit tests 157/157

[codecov]

Codecov Report

❌ Patch coverage is 41.20879% with 321 lines in your changes missing coverage. Please review.
✅ Project coverage is 17.49%. Comparing base (1a4ecd1) to head (06be54b).

Files with missing lines	Patch %	Lines
src/djehuty/web/ui.py	40.05%	231 Missing and 7 partials ⚠️
src/djehuty/utils/convenience.py	33.33%	56 Missing and 2 partials ⚠️
src/djehuty/utils/rdf.py	56.89%	23 Missing and 2 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #185   +/-   ##
=======================================
  Coverage   17.49%   17.49%           
=======================================
  Files          21       21           
  Lines       10217    10217           
  Branches     1977     1977           
=======================================
  Hits         1787     1787           
  Misses       8241     8241           
  Partials      189      189           

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