[Epic] GSAK filter parity — gap analysis & roadmap

[AgreeDK]

Background

Following Facebook/community feedback (incl. #673 and Brian Hart's comment)
requesting more GSAK-style filter capabilities. This issue tracks a full
gap analysis between OpenSAK's filter dialog and GSAK's, based on 9
screenshots of GSAK's filter dialog compared against the current
filter_dialog.py/filters/engine.py implementation.

This is a tracking issue, not something to implement in one go. Individual
checklist items should be split into their own issue when picked up (per
usual workflow — issue created just before the code, not all at once).

Already at parity (no action needed)

• Attributes tab: full parity — tri-state Yes/No/Any per attribute +
  ALL/ANY-of mode toggle
• General tab covers: name, GC code, placed-by, owner, cache type, size,
  D/T (as a from/to range — arguably more flexible than GSAK's single
  operator), distance, found/availability, premium, trackables present,
  corrected coordinates
• Misc tab covers: country/state/county, user flag, DNF, first-to-find,
  favorite points
• Polygon/line filtering — already tracked in Allow filtering by polygon #680 and Support for Custom Polygons for Challenges #184, not
  duplicated here

Gaps

1. Text-field operators (core of Brian Hart's comment on #673)

Every text field (name, owner, placed-by, country/state/county, GC code)
only supports "Contains". GSAK offers Contains / Does not contain /
Equals / Does not equal / Empty / Not empty / RegEx per field.

2. Global "Invert filter" checkbox

GSAK's General tab has a top-level "Reverse filter" checkbox that negates
the entire filter set at once. This is a general-purpose way to cover most
"hide X" requests (e.g. the "hide my own caches" request) without adding a
dedicated operator to every single field.

3. Logs tab — missing entirely

Log date, log-type checkboxes (Found it, DNF, Archive, Announcement,
Needs Maintenance, etc.), search-in-logs scope, "logged by" a specific
person (exact match / wildcard / regex / GC login ID).

4. Children tab — missing entirely

Filter the cache list by child-waypoint properties: code, type, date,
name, comment, created-by-user, count.

5. Custom tab — missing entirely

User-defined custom fields. Requires a schema change (custom field
definitions), larger separate feature — lowest priority of this list.

6. Dates tab — 4 of 8 GSAK date fields missing

Have: placed date, found date, DNF date, last log date.
Missing: created date, last GPX import date, last updated-by-user date,
last modified date.

7. Smaller field gaps

• Direction-from-center-point filter (NW/N/NE/E/SE/S/SW/W)
• "Found by me X times" (count-based; found_log_count already exists on
  the model)
• "Has child waypoints" yes/no
• "Has personal notes" yes/no
• Trackable name search (currently only has/doesn't-have)
• RegEx toggle on the Text Search tab

Out of scope for this issue

• Polygon/line filtering (Allow filtering by polygon #680, Support for Custom Polygons for Challenges #184)
• Filter Functions #673's original ask (all-in-filter behavior when no filter is set) —
  separate, unrelated bug/UX issue

Suggested next steps

• Split out "text-field operators" as its own issue (likely the
  highest-impact item)
• Split out "global invert filter" as its own issue
• Split out "Logs tab" as its own issue
• Split out "Children tab" as its own issue
• Evaluate "Custom tab" — likely deferred, larger scope
• Split out remaining Dates-tab fields as its own issue
• Split out smaller field gaps, group as convenient

[AgreeDK]