feat(diva): implement Diva Defense (UD) system

Add full Diva Defense / United Defense system: schema, repo layer,
i18n bead names, and RE-verified packet handler implementations.

Schema (0011_diva.sql): diva_beads, diva_beads_assignment,
diva_beads_points, diva_prizes tables; interception_maps/points
columns on guilds and guild_characters.

Seed (DivaDefaults.sql): 26 prize milestones for personal and
guild reward tracks (item_type=26 diva coins).

Repo (DivaRepo): 11 new methods covering bead assignment, point
accumulation, interception point tracking, prize queries, and
cleanup. Mocks wired in test_helpers_test.go.

i18n: Bead struct with EN/JP names for all 18 bead types (IDs
1–25). Session tracks currentBeadIndex (-1 = none assigned).

Packet handlers corrected against mhfo-hd.dll RE findings:
- GetKijuInfo: u8 count, 512-byte desc, color_id+bead_type per entry
- SetKiju: 1-byte ACK; persists bead assignment to DB
- GetUdMyPoint: 8×18-byte entries, no count prefix
- GetUdTotalPointInfo: u8 error + u64[64] + u8[64] + u64 (~585 B)
- GetUdSelectedColorInfo: u8 error + u8[8] = 9 bytes
- GetUdDailyPresentList: correct u16 count format (was wrong hex)
- GetUdNormaPresentList: correct u16 count format (was wrong hex)
- GetUdRankingRewardList: correct u16 count with u32 item_id/qty
- GetRewardSong: 22-byte layout with 0xFFFFFFFF prayer_end sentinel
- AddRewardSongCount: parse implemented (was NOT IMPLEMENTED stub)

server/migrations/sql/0011_diva.sql

@@ -0,0 +1,44 @@
+-- Diva Defense (United Defense) extended schema.
+-- Adds bead selection, per-bead point accumulation, interception points,
+-- and prize reward tables for personal and guild tracks.
+
+-- Interception map data per guild (binary blob, existing column pattern).
+ALTER TABLE guilds ADD COLUMN IF NOT EXISTS interception_maps bytea;
+
+-- Per-character interception points keyed by quest file ID.
+ALTER TABLE guild_characters ADD COLUMN IF NOT EXISTS interception_points jsonb NOT NULL DEFAULT '{}';
+
+-- Prize reward table for personal and guild tracks.
+CREATE TABLE IF NOT EXISTS diva_prizes (
+    id         SERIAL PRIMARY KEY,
+    type       VARCHAR(10) NOT NULL CHECK (type IN ('personal', 'guild')),
+    points_req INTEGER NOT NULL,
+    item_type  INTEGER NOT NULL,
+    item_id    INTEGER NOT NULL,
+    quantity   INTEGER NOT NULL,
+    gr         BOOLEAN NOT NULL DEFAULT false,
+    repeatable BOOLEAN NOT NULL DEFAULT false
+);
+
+-- Active bead types for the current Diva Defense event.
+CREATE TABLE IF NOT EXISTS diva_beads (
+    id   SERIAL PRIMARY KEY,
+    type INTEGER NOT NULL
+);
+
+-- Per-character bead slot assignments with expiry.
+CREATE TABLE IF NOT EXISTS diva_beads_assignment (
+    id           SERIAL PRIMARY KEY,
+    character_id INTEGER NOT NULL REFERENCES characters(id) ON DELETE CASCADE,
+    bead_index   INTEGER NOT NULL,
+    expiry       TIMESTAMPTZ NOT NULL
+);
+
+-- Per-character bead point accumulation log.
+CREATE TABLE IF NOT EXISTS diva_beads_points (
+    id           SERIAL PRIMARY KEY,
+    character_id INTEGER NOT NULL REFERENCES characters(id) ON DELETE CASCADE,
+    bead_index   INTEGER NOT NULL,
+    points       INTEGER NOT NULL,
+    timestamp    TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);