feat: initial scaffold kanban_cpp v0.1.0

C++ ImGui kanban for steering LLM agents. Six panels (Board, Calendar,
Dashboard, Agent runs, Worktrees, DoD inspector) wired to registry
functions http_request, kpi_card, sparkline, agent_runs_timeline,
dod_evidence_panel. Backend Go on :8403 (independent operations.db from
kanban_web).

backend/migrations/001_init.sql

@@ -0,0 +1,51 @@
+CREATE TABLE IF NOT EXISTS columns (
+    id          TEXT PRIMARY KEY,
+    name        TEXT NOT NULL,
+    position    INTEGER NOT NULL DEFAULT 0,
+    location    TEXT NOT NULL DEFAULT 'board' CHECK(location IN ('board','sidebar')),
+    width       INTEGER NOT NULL DEFAULT 300,
+    wip_limit   INTEGER NOT NULL DEFAULT 0,
+    created_at  TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS cards (
+    id          TEXT PRIMARY KEY,
+    requester   TEXT NOT NULL DEFAULT '',
+    title       TEXT NOT NULL,
+    description TEXT NOT NULL DEFAULT '',
+    color       TEXT NOT NULL DEFAULT '',
+    column_id   TEXT NOT NULL REFERENCES columns(id) ON DELETE CASCADE,
+    position    INTEGER NOT NULL DEFAULT 0,
+    locked      INTEGER NOT NULL DEFAULT 0,
+    created_at  TEXT NOT NULL,
+    updated_at  TEXT NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS card_column_history (
+    id         TEXT PRIMARY KEY,
+    card_id    TEXT NOT NULL REFERENCES cards(id) ON DELETE CASCADE,
+    column_id  TEXT NOT NULL,
+    entered_at TEXT NOT NULL,
+    exited_at  TEXT
+);
+
+CREATE TABLE IF NOT EXISTS card_lock_history (
+    id         TEXT PRIMARY KEY,
+    card_id    TEXT NOT NULL REFERENCES cards(id) ON DELETE CASCADE,
+    locked_at  TEXT NOT NULL,
+    unlocked_at TEXT
+);
+
+CREATE TABLE IF NOT EXISTS users (
+    id            TEXT PRIMARY KEY,
+    username      TEXT NOT NULL UNIQUE,
+    password_hash TEXT NOT NULL,
+    display_name  TEXT NOT NULL DEFAULT '',
+    created_at    TEXT NOT NULL
+);
+
+CREATE INDEX IF NOT EXISTS idx_cards_column ON cards(column_id);
+CREATE INDEX IF NOT EXISTS idx_cards_position ON cards(column_id, position);
+CREATE INDEX IF NOT EXISTS idx_history_card ON card_column_history(card_id);
+CREATE INDEX IF NOT EXISTS idx_columns_position ON columns(position);
+CREATE INDEX IF NOT EXISTS idx_lock_history_card ON card_lock_history(card_id);

backend/migrations/002_add_stickers.sql

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+-- Add stickers column to cards. Idempotent ALTER pattern in db.go ensureColumns.
+-- Stickers persist as JSON array: [{"emoji":"🔥","x":0.5,"y":0.5}, ...]
+-- x, y in [0, 1] relative to card dimensions for resize survival.
+ALTER TABLE cards ADD COLUMN stickers TEXT NOT NULL DEFAULT '[]';

backend/migrations/003_columns_extras.sql

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+-- Columnas extra de `columns` (location, width, wip_limit, is_done).
+-- Antes vivian en ensureColumns Go. Reextraidas a migration por consistencia.
+ALTER TABLE columns ADD COLUMN location  TEXT NOT NULL DEFAULT 'board';
+ALTER TABLE columns ADD COLUMN width     INTEGER NOT NULL DEFAULT 300;
+ALTER TABLE columns ADD COLUMN wip_limit INTEGER NOT NULL DEFAULT 0;
+ALTER TABLE columns ADD COLUMN is_done   INTEGER NOT NULL DEFAULT 0;

backend/migrations/004_cards_extras.sql

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+-- Columnas extra de `cards` (color, locked, assignee_id, completed_at, deleted_at, tags).
+-- Antes vivian en ensureColumns Go. La columna stickers va aparte en 002.
+ALTER TABLE cards ADD COLUMN color        TEXT    NOT NULL DEFAULT '';
+ALTER TABLE cards ADD COLUMN locked       INTEGER NOT NULL DEFAULT 0;
+ALTER TABLE cards ADD COLUMN assignee_id  TEXT;
+ALTER TABLE cards ADD COLUMN completed_at TEXT;
+ALTER TABLE cards ADD COLUMN deleted_at   TEXT;
+ALTER TABLE cards ADD COLUMN tags         TEXT    NOT NULL DEFAULT '[]';
+CREATE INDEX IF NOT EXISTS idx_cards_assignee ON cards(assignee_id);

backend/migrations/005_history_actor.sql

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+-- actor_id en histories (quien movió la card / quien bloqueó).
+ALTER TABLE card_column_history ADD COLUMN actor_id TEXT;
+ALTER TABLE card_lock_history   ADD COLUMN actor_id TEXT;

backend/migrations/006_user_color.sql

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+-- Color del avatar del usuario (Mantine color name o '#rrggbb' personalizado).
+ALTER TABLE users ADD COLUMN color TEXT NOT NULL DEFAULT '';

backend/migrations/007_card_events.sql

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+-- Eventos cronologicos por card. Complementa column_history (moves) y lock_history (locks).
+-- Captura: created, assigned, unassigned, title_changed, description_changed, color_changed, tags_changed.
+CREATE TABLE IF NOT EXISTS card_events (
+    id         TEXT PRIMARY KEY,
+    card_id    TEXT NOT NULL REFERENCES cards(id) ON DELETE CASCADE,
+    kind       TEXT NOT NULL,
+    actor_id   TEXT,
+    payload    TEXT NOT NULL DEFAULT '{}',
+    created_at TEXT NOT NULL
+);
+CREATE INDEX IF NOT EXISTS idx_card_events_card ON card_events(card_id, created_at);

backend/migrations/008_card_seq_num.sql

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+-- ID secuencial humano por card. Distinto del id hex (PK interna).
+-- Backfill por orden de creacion.
+ALTER TABLE cards ADD COLUMN seq_num INTEGER NOT NULL DEFAULT 0;
+UPDATE cards SET seq_num = (
+    SELECT COUNT(*) FROM cards c2 WHERE c2.created_at <= cards.created_at
+) WHERE seq_num = 0;
+CREATE UNIQUE INDEX IF NOT EXISTS idx_cards_seq_num ON cards(seq_num) WHERE seq_num > 0;

backend/migrations/009_card_deadline.sql

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+-- Deadline opcional por card. Fecha RFC3339 (precision dia o instante).
+-- NULL = sin deadline (default). El frontend muestra countdown hasta la fecha.
+ALTER TABLE cards ADD COLUMN deadline TEXT;
+CREATE INDEX IF NOT EXISTS idx_cards_deadline ON cards(deadline) WHERE deadline IS NOT NULL;

backend/migrations/010_card_messages.sql

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+-- Per-card chat messages (human-to-human comments).
+-- Distinct from card_events (which records system events like title_changed)
+-- and from /api/chat (which is the board-level LLM chat).
+
+CREATE TABLE IF NOT EXISTS card_messages (
+    id          TEXT PRIMARY KEY,
+    card_id     TEXT NOT NULL,
+    author_id   TEXT,
+    body        TEXT NOT NULL,
+    created_at  TEXT NOT NULL,
+    FOREIGN KEY (card_id) REFERENCES cards(id) ON DELETE CASCADE
+);
+
+CREATE INDEX IF NOT EXISTS idx_card_messages_card ON card_messages(card_id, created_at);