feat: add database schema and SQLx migrations

- 5 reversible migrations: extensions/enums, tables, indexes, views, config seed
- Tables: event, user, session, upload, hashtag, upload_hashtag, comment,
  comment_hashtag, like, export_job, config
- Views: v_feed (uploads with like/comment counts), v_hashtag_counts
- Indexes optimised for feed queries, session lookup, hashtag filtering
- Config table seeded with default rate limits and quotas
- db.rs module: PgPool creation with auto-migration on startup
- docker-compose.override.yml: expose db port 5432 for local dev
- Fix crate names: async_zip, tower_governor (underscore, not hyphen)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/migrations/002_tables.up.sql

@@ -0,0 +1,112 @@
+-- event
+CREATE TABLE event (
+    id                  UUID        PRIMARY KEY DEFAULT gen_random_uuid(),
+    slug                TEXT        NOT NULL UNIQUE,
+    name                TEXT        NOT NULL,
+    cover_image_path    TEXT,
+    is_active           BOOLEAN     NOT NULL DEFAULT TRUE,
+    uploads_locked_at   TIMESTAMPTZ,
+    export_released_at  TIMESTAMPTZ,
+    export_zip_ready    BOOLEAN     NOT NULL DEFAULT FALSE,
+    export_html_ready   BOOLEAN     NOT NULL DEFAULT FALSE,
+    created_at          TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- user
+CREATE TABLE "user" (
+    id                  UUID        PRIMARY KEY DEFAULT gen_random_uuid(),
+    event_id            UUID        NOT NULL REFERENCES event(id) ON DELETE CASCADE,
+    display_name        TEXT        NOT NULL,
+    role                user_role   NOT NULL DEFAULT 'guest',
+    is_banned           BOOLEAN     NOT NULL DEFAULT FALSE,
+    uploads_hidden      BOOLEAN     NOT NULL DEFAULT FALSE,
+    recovery_pin_hash   TEXT        NOT NULL,
+    total_upload_bytes  BIGINT      NOT NULL DEFAULT 0,
+    created_at          TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- session
+CREATE TABLE session (
+    id           UUID        PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id      UUID        NOT NULL REFERENCES "user"(id) ON DELETE CASCADE,
+    token_hash   TEXT        NOT NULL UNIQUE,
+    expires_at   TIMESTAMPTZ NOT NULL,
+    last_seen_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    created_at   TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- upload
+CREATE TABLE upload (
+    id                  UUID        PRIMARY KEY DEFAULT gen_random_uuid(),
+    event_id            UUID        NOT NULL REFERENCES event(id) ON DELETE CASCADE,
+    user_id             UUID        NOT NULL REFERENCES "user"(id),
+    original_path       TEXT        NOT NULL,
+    preview_path        TEXT,
+    thumbnail_path      TEXT,
+    mime_type           TEXT        NOT NULL,
+    original_size_bytes BIGINT      NOT NULL,
+    caption             TEXT,
+    created_at          TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    deleted_at          TIMESTAMPTZ
+);
+
+-- hashtag
+CREATE TABLE hashtag (
+    id         UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    event_id   UUID NOT NULL REFERENCES event(id) ON DELETE CASCADE,
+    tag        TEXT NOT NULL,
+    UNIQUE (event_id, tag)
+);
+
+-- upload_hashtag (junction)
+CREATE TABLE upload_hashtag (
+    upload_id   UUID NOT NULL REFERENCES upload(id) ON DELETE CASCADE,
+    hashtag_id  UUID NOT NULL REFERENCES hashtag(id) ON DELETE CASCADE,
+    PRIMARY KEY (upload_id, hashtag_id)
+);
+
+-- comment
+CREATE TABLE comment (
+    id          UUID        PRIMARY KEY DEFAULT gen_random_uuid(),
+    upload_id   UUID        NOT NULL REFERENCES upload(id) ON DELETE CASCADE,
+    user_id     UUID        NOT NULL REFERENCES "user"(id),
+    body        TEXT        NOT NULL,
+    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    deleted_at  TIMESTAMPTZ
+);
+
+-- comment_hashtag (junction)
+CREATE TABLE comment_hashtag (
+    comment_id  UUID NOT NULL REFERENCES comment(id) ON DELETE CASCADE,
+    hashtag_id  UUID NOT NULL REFERENCES hashtag(id) ON DELETE CASCADE,
+    PRIMARY KEY (comment_id, hashtag_id)
+);
+
+-- like
+CREATE TABLE "like" (
+    upload_id   UUID        NOT NULL REFERENCES upload(id) ON DELETE CASCADE,
+    user_id     UUID        NOT NULL REFERENCES "user"(id) ON DELETE CASCADE,
+    created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    PRIMARY KEY (upload_id, user_id)
+);
+
+-- export_job
+CREATE TABLE export_job (
+    id            UUID           PRIMARY KEY DEFAULT gen_random_uuid(),
+    event_id      UUID           NOT NULL REFERENCES event(id) ON DELETE CASCADE,
+    type          export_type    NOT NULL,
+    status        export_status  NOT NULL DEFAULT 'pending',
+    progress_pct  SMALLINT       NOT NULL DEFAULT 0 CHECK (progress_pct BETWEEN 0 AND 100),
+    file_path     TEXT,
+    error_message TEXT,
+    created_at    TIMESTAMPTZ    NOT NULL DEFAULT NOW(),
+    completed_at  TIMESTAMPTZ,
+    UNIQUE (event_id, type)
+);
+
+-- config (admin-configurable runtime settings)
+CREATE TABLE config (
+    key        TEXT        PRIMARY KEY,
+    value      TEXT        NOT NULL,
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);