Fixes

• Fix: web plugin helpers httputils.serve_resource/serve_folder ignored their mimetypes and fallback_mimetype parameters and always used the built-in mapping, so custom web plugins could not serve additional file types with a correct Content-Type
• Fix: free-busy REPORT always failed with HTTP 400 ("FREEBUSY occurrences limit of 0 hit") when [reporting] max_freebusy_occurrence is set to 0 (limit disabled), because the limit check did not honor the disabled limit
• Fix: time-range filter treated a VEVENT with a whole-day DURATION (e.g. P1D, P2D) as zero-length (timedelta.seconds instead of total_seconds), so such events were missing from calendar-query REPORT results
• Fix: calendar-data expand (REPORT) left recurrence properties (e.g. RDATE) on the expanded single-occurrence VEVENTs; a single try/except around the sequential delattr() calls stopped at the first absent property (e.g. missing EXDATE), so later ones were never removed
• Fix: text-match filter on a structured property (e.g. vCard N or ADR) crashed with HTTP 500 (AttributeError: 'Name'/'Address' object has no attribute 'lower') because vobject parses these into non-string objects; their text representation is now used
• Fix: sharing bday-to-ICS conversion assigned the empty-FN fallback marker to the {nickname} placeholder instead of {fn}, so a VCARD with an empty FN got its NICKNAME overwritten with "!fn!" in the generated SUMMARY/DESCRIPTION and the {fn} fallback never resolved
• Fix: sharing/delete: add forgotten backmap