chore(merge): merge develop into main for 9.4.0 cycle

Brings 53 develop commits (i18n, Diva, campaign, guild invites, save
transfer, return/rookie guilds, hunting tournament, JSON quest/scenario
loaders, Ghidra-derived user binary parsing, and misc fixes) onto main
now that 9.3.2 has been tagged and released.

Resolves two overlap zones:

1. Migration number collision. Main shipped 0010_fix_zero_rasta_id and
   0011_fix_stale_boost_time in 9.3.2; develop had independently
   numbered 0010_campaign..0015_tournament. The migration runner keys
   applied versions by integer, so coexisting files with the same
   numeric prefix would silently skip each other. Develop's files have
   been renumbered to 0016..0021, leaving main's 0010/0011 intact. A
   schema_version rename script is required on any server that had
   already applied the old develop numbers (only frontier.mogapedia.fr
   at the time of this merge).

2. CHANGELOG.md. Develop's in-progress feature entries move into
   [Unreleased] with updated migration references; the [9.3.2] section
   is preserved verbatim.

main.go version string bumped to 9.4.0-dev to mark the new cycle.

Full test suite (go test -race ./...) passes.

README.md

@@ -100,6 +100,18 @@ These files contain quest definitions and scenario data that the server sends to
 
 **Without these files, quests will not load and the client will crash.**
 
+### JSON Format Support
+
+As an alternative to opaque `.bin` files, Erupe supports human-readable `.json` files for quests, scenarios, and Hunting Road config. The server always tries `.bin` first and falls back to `.json` automatically — existing binary files work unchanged.
+
+| File type | Location | Documentation |
+|-----------|----------|---------------|
+| Quest | `bin/quests/<name>.json` | Erupe wiki |
+| Scenario | `bin/scenarios/<name>.json` | `docs/scenario-format.md` |
+| Hunting Road | `bin/rengoku_data.json` | Erupe wiki |
+
+JSON quests and scenarios use UTF-8 text (converted to Shift-JIS on the wire), making them diff-friendly and editable without binary tools.
+
 ## Client Setup
 
 1. Obtain a Monster Hunter Frontier client (version G10 or later recommended)
@@ -149,6 +161,64 @@ Edit `config.json` before starting the server. The essential settings are:
 
 `config.example.json` is intentionally minimal — all other settings have sane defaults built into the server. For the full configuration reference (gameplay multipliers, debug options, Discord integration, in-game commands, entrance/channel definitions), see [config.reference.json](./config.reference.json) and the [Erupe Wiki](https://github.com/Mezeporta/Erupe/wiki).
 
+## Save Transfers
+
+To move a character from one Erupe instance to another, use the `saveutil` admin tool.
+
+### Build saveutil
+
+```bash
+go build -o saveutil ./cmd/saveutil/
+```
+
+### Method 1: Direct admin import (recommended)
+
+This method does not require the server to be running.
+
+**On the source server**, export the character:
+```bash
+./saveutil export --config config.json --char-id <SOURCE_ID> --output my_character.json
+```
+
+**On the destination server**, find the target character ID (use pgAdmin or `psql`), then import:
+```bash
+./saveutil import --config config.json --char-id <DEST_ID> --file my_character.json
+```
+
+### Method 2: Player self-service via API
+
+This method lets players import their own save without admin DB access, but requires the admin to grant a one-time token first.
+
+**Admin step** — grant a token (valid for 24 hours by default):
+```bash
+./saveutil grant-import --config config.json --char-id <DEST_ID> [--ttl 48h]
+# → Import token for character 42: abc123...
+```
+
+Give the printed token to the player. They then call the import endpoint:
+```bash
+curl -X POST http://<server>:8080/v2/characters/<DEST_ID>/import \
+  -H "Authorization: Bearer <player_token>" \
+  -H "Content-Type: application/json" \
+  -d '{
+    "import_token": "<admin_token>",
+    "character": <paste contents of my_character.json .character field here>
+  }'
+```
+
+The token is consumed on success and cannot be reused. To cancel a pending grant:
+```bash
+./saveutil revoke-import --config config.json --char-id <DEST_ID>
+```
+
+### Troubleshooting
+
+**"savedata integrity check failed"** — the character was imported directly into the DB without going through `saveutil`. Fix by clearing the stored hash:
+```sql
+UPDATE characters SET savedata_hash = NULL WHERE id = <char_id>;
+```
+The correct hash will be recomputed on the next save.
+
 ## Features
 
 - **Multi-version Support**: Compatible with all Monster Hunter Frontier versions from Season 6.0 to ZZ
@@ -270,4 +340,4 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines.
 
 ## Authors
 
-A list of authors can be found at [AUTHORS.md](AUTHORS.md).
+A list of authors can be found at [HISTORY.md](HISTORY.md).