NCE-21 NCE-27: improve route filter behavior

[FortPT]

Implements NCE-21 and NCE-27.

• Display All Events when all route statuses or severities are selected.
• Preserve individual values for partial selections.
• Prevent the same status or severity from being selected in both Include and Exclude.
• Exclude wins when opening an existing legacy conflicting configuration.
• Select All respects disabled conflicting values.

Validation:

• 23 focused WebUI/routing tests passed.
• Python compile check passed.
• app.js syntax passed.
• qa_patch.js syntax passed.
• git diff --check passed.

Keep draft until Development validation completes.