feat: GeoIP-based geo detection + configurable rename template

- Add MaxMind GeoLite2-City mmdb auto-download and IP-based geo lookup
  (covers all 249 countries globally, replacing limited 8-country regex)
- Add RenameOptions with 5 toggleable fields (flag/alias/country/city/index)
  stored as rename_options_json on collections
- Collection rename pipeline uses DetectGeoWithServer(name, server) which
  tries GeoIP lookup first, falls back to name-based regex matching
- Chinese country/city names + emoji flag prefix
- Country-city dedup: skip city when it equals country (e.g. 香港/香港)
- URI fragment encoding: url.QueryEscape -> url.PathEscape (%20 not +)
- Egress cache key excludes name field so renamed nodes still match cache
- Frontend: 5 toggle buttons in collection edit form, default all on
- Migrations: 0004 (source alias + collection rename_enabled),
  0005 (collection rename_options_json)

go.sum

@@ -45,6 +45,8 @@ github.com/mfridman/interpolate v0.0.2 h1:pnuTK7MQIxxFz1Gr+rjSIx9u7qVjf5VOoM/u6B
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 github.com/ncruces/go-strftime v1.0.0/go.mod h1:Fwc5htZGVVkseilnfgOVb9mKy6w1naJmn9CehxcKcls=
+github.com/oschwald/maxminddb-golang v1.13.1 h1:G3wwjdN9JmIK2o/ermkHM+98oX5fS+k5MbwsmL4MRQE=
+github.com/oschwald/maxminddb-golang v1.13.1/go.mod h1:K4pgV9N/GcK694KSTmVSDTODk4IsCNThNdTmnaBZ/F8=
 github.com/pelletier/go-toml/v2 v2.2.4 h1:mye9XuhQ6gvn5h28+VilKrrPoQVanw5PMw/TB0t5Ec4=
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 github.com/philhofer/fwd v1.2.0 h1:e6DnBTl7vGY+Gz322/ASL4Gyp1FspeMvx1RNDoToZuM=