feat: initial commit

Axum/Postgres server with auth, migrations, and Docker setup.

migrations/20260812130000_create_conversations.up.sql

@@ -0,0 +1,23 @@
+CREATE TYPE conversation_kind AS ENUM ('dm', 'group', 'channel');
+
+CREATE TABLE conversations (
+    id           UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    workspace_id UUID REFERENCES workspaces(id) ON DELETE CASCADE,
+    kind         conversation_kind NOT NULL,
+    name         TEXT,
+    is_public    BOOLEAN NOT NULL DEFAULT true,
+    created_by   UUID NOT NULL REFERENCES users(id),
+    created_at   TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at   TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    deleted_at   TIMESTAMPTZ
+);
+
+CREATE TABLE conversation_members (
+    conversation_id UUID        NOT NULL REFERENCES conversations(id) ON DELETE CASCADE,
+    user_id         UUID        NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    joined_at       TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    PRIMARY KEY (conversation_id, user_id)
+);
+
+CREATE INDEX conversations_workspace_id_idx       ON conversations(workspace_id);
+CREATE INDEX conversation_members_user_id_idx     ON conversation_members(user_id);