Avoid implicit file reads from string calendar input

[uwezkhan]

This PR hardens Component.from_ical() by removing ambiguous string-path handling.

Previously, a newline-free str passed to from_ical() was treated as a possible filesystem path. If that path existed, the parser read the file contents automatically. This made it easy for applications that pass untrusted strings into Calendar.from_ical() / Component.from_ical() to accidentally allow local file reads or file-content disclosure through parser errors.

After this change:

• Path input still reads an iCalendar file explicitly.
• bytes and str input are treated only as iCalendar payload data.
• Regression tests verify string paths are not read and file contents are not leaked.

[read-the-docs-community]

Documentation build overview

📚 icalendar | 🛠️ Build #32720441 | 📁 Comparing a8e899d against latest (7357cec)

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15 files changed · ± 15 modified

± Modified

• 404.html
• genindex.html
• contribute/index.html
• contribute/maintenance.html
• reference/changelog.html
• reference/api/icalendar.cal.alarm.html
• reference/api/icalendar.cal.component.html
• reference/api/icalendar.prop.dt.html
• reference/api/icalendar.prop.dt.period.html
• reference/api/icalendar.prop.recur.html
• and 5 more...