feat(users): implement user following system and following feed

Add follow/unfollow actions and social stats to user profiles
Introduce Following feed scope in Life view
Add notifications for new followers

backend/db/schema.sql

@@ -94,6 +94,17 @@ CREATE UNIQUE INDEX IF NOT EXISTS users_referral_code_idx
 CREATE INDEX IF NOT EXISTS users_referred_by_user_id_idx
   ON users(referred_by_user_id);
 
+CREATE TABLE IF NOT EXISTS user_follows (
+  follower_user_id integer NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  followed_user_id integer NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  created_at timestamptz NOT NULL DEFAULT now(),
+  PRIMARY KEY (follower_user_id, followed_user_id),
+  CHECK (follower_user_id <> followed_user_id)
+);
+
+CREATE INDEX IF NOT EXISTS user_follows_followed_created_idx
+  ON user_follows(followed_user_id, created_at DESC, follower_user_id);
+
 CREATE TABLE IF NOT EXISTS environments (
   id integer GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
   name text NOT NULL UNIQUE,
@@ -290,6 +301,7 @@ VALUES
   ('life.comments.delete-any', 'Delete any Life comment', 'Delete any Life comment.', 'Life', true),
   ('life.reactions.set', 'Set Life reactions', 'Set and remove Life reactions.', 'Life', true),
   ('life.ratings.set', 'Set Life ratings', 'Set and remove Life star ratings.', 'Life', true),
+  ('users.follow', 'Follow users', 'Follow and unfollow public user profiles.', 'Users', true),
   ('discussions.comments.create', 'Create discussion comments', 'Create entity discussion comments and replies.', 'Discussions', true),
   ('discussions.comments.delete', 'Delete own discussion comments', 'Delete own entity discussion comments.', 'Discussions', true),
   ('discussions.comments.delete-any', 'Delete any discussion comment', 'Delete any entity discussion comment.', 'Discussions', true)
@@ -381,6 +393,7 @@ JOIN permissions p ON p.key = ANY (ARRAY[
   'life.comments.delete-any',
   'life.reactions.set',
   'life.ratings.set',
+  'users.follow',
   'discussions.comments.create',
   'discussions.comments.delete',
   'discussions.comments.delete-any'
@@ -449,6 +462,7 @@ JOIN permissions p ON p.key = ANY (ARRAY[
   'life.comments.delete',
   'life.reactions.set',
   'life.ratings.set',
+  'users.follow',
   'discussions.comments.create',
   'discussions.comments.delete'
 ])
@@ -496,6 +510,7 @@ JOIN permissions p ON p.key = ANY (ARRAY[
   'life.comments.delete',
   'life.reactions.set',
   'life.ratings.set',
+  'users.follow',
   'discussions.comments.create',
   'discussions.comments.delete'
 ])
@@ -514,6 +529,13 @@ JOIN permissions p ON p.key = 'life.ratings.set'
 WHERE r.key IN ('admin', 'editor', 'member')
 ON CONFLICT DO NOTHING;
 
+INSERT INTO role_permissions (role_id, permission_id)
+SELECT r.id, p.id
+FROM roles r
+JOIN permissions p ON p.key = 'users.follow'
+WHERE r.key IN ('admin', 'editor', 'member')
+ON CONFLICT DO NOTHING;
+
 WITH first_owner_user AS (
   SELECT u.id
   FROM users u
@@ -1231,10 +1253,12 @@ CREATE TABLE IF NOT EXISTS notifications (
       'life_comment_reply',
       'discussion_comment_reply',
       'life_post_reaction',
+      'user_follow',
       'moderation_result'
     )
   ),
   life_post_id integer REFERENCES life_posts(id) ON DELETE CASCADE,
+  profile_user_id integer REFERENCES users(id) ON DELETE CASCADE,
   life_comment_id integer REFERENCES life_post_comments(id) ON DELETE CASCADE,
   parent_life_comment_id integer REFERENCES life_post_comments(id) ON DELETE SET NULL,
   discussion_comment_id integer REFERENCES entity_discussion_comments(id) ON DELETE CASCADE,
@@ -1274,6 +1298,13 @@ CREATE UNIQUE INDEX IF NOT EXISTS notifications_life_post_reaction_unique_idx
   ON notifications(recipient_user_id, actor_user_id, life_post_id)
   WHERE type = 'life_post_reaction' AND actor_user_id IS NOT NULL AND life_post_id IS NOT NULL;
 
+ALTER TABLE notifications
+  ADD COLUMN IF NOT EXISTS profile_user_id integer REFERENCES users(id) ON DELETE CASCADE;
+
+CREATE UNIQUE INDEX IF NOT EXISTS notifications_user_follow_unique_idx
+  ON notifications(recipient_user_id, actor_user_id, profile_user_id)
+  WHERE type = 'user_follow' AND actor_user_id IS NOT NULL AND profile_user_id IS NOT NULL;
+
 CREATE TABLE IF NOT EXISTS notification_ws_tickets (
   id integer GENERATED BY DEFAULT AS IDENTITY PRIMARY KEY,
   user_id integer NOT NULL REFERENCES users(id) ON DELETE CASCADE,
@@ -1289,6 +1320,24 @@ CREATE INDEX IF NOT EXISTS notification_ws_tickets_user_idx
 ALTER TABLE notifications
   ADD COLUMN IF NOT EXISTS moderation_reason text;
 
+ALTER TABLE notifications
+  ADD COLUMN IF NOT EXISTS profile_user_id integer REFERENCES users(id) ON DELETE CASCADE;
+
+ALTER TABLE notifications
+  DROP CONSTRAINT IF EXISTS notifications_type_check;
+
+ALTER TABLE notifications
+  ADD CONSTRAINT notifications_type_check CHECK (
+    type IN (
+      'life_post_comment',
+      'life_comment_reply',
+      'discussion_comment_reply',
+      'life_post_reaction',
+      'user_follow',
+      'moderation_result'
+    )
+  );
+
 ALTER TABLE life_tags
   ADD COLUMN IF NOT EXISTS is_rateable boolean NOT NULL DEFAULT false;