chore: PostgreSQL migration compatibility and infrastructure improvements

Database & Migrations:
- Update all Alembic migrations for PostgreSQL compatibility
- Remove SQLite-specific syntax (AUTOINCREMENT, etc.)
- Add database utility helpers for PostgreSQL operations
- Fix services to use PostgreSQL-compatible queries

Documentation:
- Add comprehensive Docker deployment guide
- Add production deployment documentation
- Add infrastructure architecture documentation
- Update database setup guide for PostgreSQL-only
- Expand troubleshooting guide

Architecture & Validation:
- Add migration.yaml rules for SQL compatibility checking
- Enhance validate_architecture.py with migration validation
- Update architecture rules to validate Alembic migrations

Development:
- Fix duplicate install-all target in Makefile
- Add Celery/Redis validation to install.py script
- Add docker-compose.test.yml for CI testing
- Add squash_migrations.py utility script
- Update tests for PostgreSQL compatibility
- Improve test fixtures in conftest.py

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/development/migration/database-migrations.md

@@ -54,6 +54,100 @@ make backup-db
 make verify-setup
 ```
 
+## Alembic Commands Explained
+
+Understanding what each Alembic command does is essential for managing database migrations effectively.
+
+### Core Commands Reference
+
+| Command | Description |
+|---------|-------------|
+| `alembic upgrade head` | Apply **all** pending migrations to get to the latest version |
+| `alembic upgrade +1` | Apply only the **next** single migration (one step forward) |
+| `alembic downgrade -1` | Roll back the **last** applied migration (one step back) |
+| `alembic downgrade base` | Roll back **all** migrations (returns to empty schema) |
+| `alembic current` | Show which migration the database is currently at |
+| `alembic history` | List all migrations in the chain |
+| `alembic heads` | Show the latest migration revision(s) |
+
+### Visual Example
+
+```
+Migration Chain:  [base] → [A] → [B] → [C] → [D] (head)
+                                  ↑
+                                  └── current database state (at revision B)
+
+Command                     Result
+─────────────────────────────────────────────────────────
+alembic upgrade head     →  Database moves to [D]
+alembic upgrade +1       →  Database moves to [C]
+alembic downgrade -1     →  Database moves to [A]
+alembic downgrade base   →  Database returns to [base] (empty schema)
+alembic current          →  Shows "B" (current revision)
+```
+
+### Makefile Shortcuts
+
+| Make Command | Alembic Equivalent | Description |
+|--------------|-------------------|-------------|
+| `make migrate-up` | `alembic upgrade head` | Apply all pending migrations |
+| `make migrate-down` | `alembic downgrade -1` | Roll back last migration |
+| `make migrate-status` | `alembic current` + `alembic history` | Show current state and history |
+
+### Additional Useful Commands
+
+```bash
+# Show detailed migration history
+alembic history --verbose
+
+# Upgrade/downgrade to a specific revision
+alembic upgrade abc123def456
+alembic downgrade abc123def456
+
+# Show what SQL would be generated (without executing)
+alembic upgrade head --sql
+
+# Mark database as being at a specific revision (without running migrations)
+alembic stamp head
+alembic stamp abc123def456
+
+# Show the current revision ID only
+alembic current --verbose
+```
+
+### Database Initialization Workflow
+
+For setting up a new database:
+
+```bash
+# Option 1: Empty schema only (just tables, no data)
+make migrate-up
+
+# Option 2: Schema + production essentials (admin user, settings, CMS, email templates)
+make init-prod
+
+# Option 3: Full development setup (schema + production data + demo data)
+make db-setup
+# Or step by step:
+make init-prod
+make seed-demo
+```
+
+### Reset Workflow
+
+For completely resetting the database:
+
+```bash
+# Nuclear reset: deletes database file, recreates schema, seeds all data
+make db-reset
+```
+
+> **Note**: `make db-reset` rolls back all migrations and recreates the schema from scratch.
+
+!!! note "PostgreSQL Required"
+    This project uses PostgreSQL exclusively. SQLite is not supported.
+    Start the development database with: `make docker-up`
+
 ## Development Workflows
 
 ### Adding New Database Fields