feat: implement database layer and rename auction -> listing

Major Changes:
- Set up SQLx database connection and migration system
- Create complete initial database schema with all tables
- Rename 'auction' to 'listing' throughout codebase for better terminology
- Update bot commands: /newauction -> /newlisting, /myauctions -> /mylistings
- Update all database tables: auctions -> listings, auction_medias -> listing_medias
- Update foreign key relationships and indexes
- Add automatic database migration on startup
- Update documentation and README
- Complete backlog tasks: task-001, task-002, task-010

The bot now has a solid database foundation ready for implementing core business logic.
All tests pass and code compiles successfully.

README.md

@@ -6,18 +6,18 @@ A Telegram bot for managing various types of auctions, built in Rust using SQLit
 
 ## Core Features
 
-### Auction Types
+### Listing Types
 1. **Standard Auctions**: Traditional time-based bidding with anti-sniping protection
 2. **Multi-slot Auctions**: Multiple winners (e.g., 3 commission slots available)
 3. **Fixed Price Sales**: Set price with limited quantity
 4. **Blind Auctions**: Bidders submit amounts with descriptions; seller chooses winner (not necessarily highest bid)
 
 ### Key Functionality
-- **Telegram Bot**: The bot is interacted with primarily through Telegram. Sellers can create auctions, and view bids on auctions. Buyers can bid on auctions and view their bids.
+- **Telegram Bot**: The bot is interacted with primarily through Telegram. Sellers can create listings, and view bids on listings. Buyers can bid on listings and view their bids.
 - **Proxy/Automatic Bidding**: Users set maximum bid; system auto-bids up to that amount
 - **Anti-sniping Protection**: Configurable time extension if bid placed in last N minutes
 - **Buy-now Option**: Instant purchase at fixed price
-- **Media Support**: Multiple images/videos per auction on the telegram post.
+- **Media Support**: Multiple images/videos per listing on the telegram post.
 - **Outbid Notifications**: Configurable user notifications
 - **Non-payment Handling**: Track failed payments, allow selection of next highest bidder
 - **Localization Support**: Multi-language structure (to be implemented)
@@ -37,11 +37,11 @@ CREATE TABLE users (
     updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
 );
 
--- Main auction table (handles all auction types)
-CREATE TABLE auctions (
+-- Main listing table (handles all listing types)
+CREATE TABLE listings (
     id INTEGER PRIMARY KEY,
     seller_id INTEGER NOT NULL,
-    auction_type TEXT NOT NULL, -- 'standard', 'multi_slot', 'fixed_price', 'blind'
+    listing_type TEXT NOT NULL, -- 'standard', 'multi_slot', 'fixed_price', 'blind'
     title TEXT NOT NULL,
     description TEXT,
 
@@ -66,7 +66,7 @@ CREATE TABLE auctions (
 -- Proxy bid strategies (NOT actual bids, but bidding strategies)
 CREATE TABLE proxy_bids (
     id INTEGER PRIMARY KEY,
-    auction_id INTEGER NOT NULL,
+    listing_id INTEGER NOT NULL,
     buyer_id INTEGER NOT NULL,
     max_amount DECIMAL(10,2) NOT NULL,
     is_active BOOLEAN DEFAULT TRUE,
@@ -74,45 +74,45 @@ CREATE TABLE proxy_bids (
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
     updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
 
-    FOREIGN KEY (auction_id) REFERENCES auctions(id),
+    FOREIGN KEY (listing_id) REFERENCES listings(id),
     FOREIGN KEY (buyer_id) REFERENCES users(id),
-    UNIQUE(auction_id, buyer_id) -- One active proxy per user per auction
+    UNIQUE(listing_id, buyer_id) -- One active proxy per user per listing
 );
 
 -- Actual bids that happened (events)
 CREATE TABLE bids (
     id INTEGER PRIMARY KEY,
-    auction_id INTEGER NOT NULL,
+    listing_id INTEGER NOT NULL,
     buyer_id INTEGER NOT NULL,
     bid_amount DECIMAL(10,2) NOT NULL,
 
-    -- For blind auctions
+    -- For blind listings
     description TEXT,
 
     -- Status
     is_cancelled BOOLEAN DEFAULT FALSE,
-    slot_number INTEGER, -- For multi-slot auctions
+    slot_number INTEGER, -- For multi-slot listings
 
     -- NULL = manual bid, NOT NULL = generated from proxy
     proxy_bid_id INTEGER,
 
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
     updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-    FOREIGN KEY (auction_id) REFERENCES auctions(id),
+    FOREIGN KEY (listing_id) REFERENCES listings(id),
     FOREIGN KEY (buyer_id) REFERENCES users(id),
     FOREIGN KEY (proxy_bid_id) REFERENCES proxy_bids(id)
 );
 
 -- Media attachments
-CREATE TABLE auction_medias (
+CREATE TABLE listing_medias (
     id INTEGER PRIMARY KEY,
-    auction_id INTEGER NOT NULL,
+    listing_id INTEGER NOT NULL,
     telegram_file_id TEXT NOT NULL,
     media_type TEXT NOT NULL, -- 'photo', 'video'
     position INTEGER DEFAULT 0,
     created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
     updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-    FOREIGN KEY (auction_id) REFERENCES auctions(id)
+    FOREIGN KEY (listing_id) REFERENCES listings(id)
 );
 
 -- User preferences
@@ -233,8 +233,8 @@ TZ=UTC
 ```
 start - Show welcome message
 help - Show help message
-newauction - Create a new auction
-myauctions - View your auctions as a seller
+newlisting - Create a new listing
+mylistings - View your listings as a seller
 mybids - View your active bids
 settings - Configure notifications
 ```
@@ -248,11 +248,11 @@ settings - Configure notifications
 
 ## Next Implementation Steps (Priority Order)
 
-### 1. Complete Auction Creation Flow
+### 1. Complete Listing Creation Flow
 - Implement multi-step wizard state machine
 - Handle media uploads (store Telegram file_ids)
 - Add validation for each field
-- Create auction in database
+- Create listing in database
 
 ### 2. Implement Bidding System
 - Place manual bid function
@@ -265,10 +265,10 @@ settings - Configure notifications
 - Auction expiry processing
 - Notification sending
 
-### 4. Auction Browsing
+### 4. Listing Browsing
 - Paginated list with filters
 - Search functionality
-- Detailed auction view with bid history
+- Detailed listing view with bid history
 
 ### 5. Admin Interface
 - Axum web server in same binary