Fix: excludedEvents matches substrings like the default calendar module (#55)

[randomBrainstormer]

Problem

Reported in #55 (and re-confirmed by a second user in 2025): excludedEvents entries don't hide matching events. Custom events work fine — only exclusion is broken.

Root cause

filterEvent() did:

this.config.excludedEvents.includes(event.summary)

Array.includes() is an exact, case-sensitive, full-title equality check. So excludedEvents: ["Birthday"] only hides an event titled exactly Birthday — never John's Birthday or birthday party. Users coming from the default MagicMirror calendar module expect case-insensitive substring matching (and the object form), which is what they configured for.

Fix

New isEventExcluded(title) helper that mirrors the default calendar module's semantics. Each excludedEvents entry may be:

• a plain string → case-insensitive substring match, or
• an object { filterBy, caseSensitive, regex } → case-sensitive and/or regex matching.

Also guards against private events (no summary) and empty/invalid filter entries.

excludedEvents: [
  "Birthday",                                  // hides any title containing "birthday"
  { filterBy: "Standup", caseSensitive: true },// exact-case substring
  { filterBy: "^\\[private\\]", regex: true }  // regex
]

Test plan

• npx jest — 29/29 pass (7 new tests: substring, exact, case-sensitive, regex, no-summary, invalid entries)
• Configure excludedEvents: ["Birthday"] and confirm "John's Birthday" no longer shows

Note: version intentionally not bumped — the auto-bump workflow handles it on merge.

Closes #55