feat: feature requests board with voting

- [FEATURES] tab next to PINNED in channel header
- Create, vote/unvote, filter by status (open/planned/done/rejected)
- Sort by vote count (most voted first)
- Status selector for moderation
- DB: feature_requests + feature_request_votes tables
- Backend: full CRUD + vote endpoints under /servers/{id}/feature-requests

internal/db/db.go

@@ -534,5 +534,27 @@ CREATE TABLE IF NOT EXISTS poll_votes (
 	UNIQUE (option_id, user_id)
 );
 CREATE INDEX IF NOT EXISTS idx_poll_votes_option ON poll_votes(option_id);
+
+-- Feature requests
+CREATE TABLE IF NOT EXISTS feature_requests (
+	id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+	server_id UUID NOT NULL REFERENCES servers(id) ON DELETE CASCADE,
+	channel_id UUID REFERENCES channels(id) ON DELETE SET NULL,
+	author_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+	title VARCHAR(255) NOT NULL,
+	description TEXT NOT NULL DEFAULT '',
+	status VARCHAR(16) NOT NULL DEFAULT 'open' CHECK (status IN ('open', 'planned', 'done', 'rejected')),
+	created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+	updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+CREATE INDEX IF NOT EXISTS idx_feature_requests_server ON feature_requests(server_id, created_at DESC);
+
+CREATE TABLE IF NOT EXISTS feature_request_votes (
+	feature_request_id UUID NOT NULL REFERENCES feature_requests(id) ON DELETE CASCADE,
+	user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+	created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+	PRIMARY KEY (feature_request_id, user_id)
+);
+CREATE INDEX IF NOT EXISTS idx_feature_request_votes_fr ON feature_request_votes(feature_request_id);
 `