Add new Mermaid diagrams for consensus algorithms and data consistency models

- Introduced multiple Mermaid diagrams illustrating key concepts in distributed systems, including sequence diagrams for consensus algorithms and flowcharts for data consistency models.
- Added diagrams for the Paxos consensus process, Raft leader election, and various consistency models such as linearizability and eventual consistency.
- Enhanced documentation clarity and visual representation of complex topics, aiding user understanding and engagement.

Author: spawn08

.mermaid_validate/b0000.mmd

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+sequenceDiagram
+  participant P as Proposer
+  participant A1 as Acceptor 1
+  participant A2 as Acceptor 2
+  participant A3 as Acceptor 3
+
+  P->>A1: Prepare(n=1)
+  P->>A2: Prepare(n=1)
+  P->>A3: Prepare(n=1)
+  A1-->>P: Promise(n=1, none)
+  A2-->>P: Promise(n=1, none)
+  Note over P: Majority promised
+  P->>A1: Accept(n=1, value=X)
+  P->>A2: Accept(n=1, value=X)
+  A1-->>P: Accepted
+  A2-->>P: Accepted
+  Note over P: Value X is chosen

.mermaid_validate/b0000.svg

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+stateDiagram-v2
+  [*] --> Follower
+  Follower --> Candidate: Election timeout
+  Candidate --> Leader: Receives majority votes
+  Candidate --> Follower: Discovers higher term
+  Leader --> Follower: Discovers higher term
+  Candidate --> Candidate: Election timeout (split vote)

.mermaid_validate/b0001.mmd

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+sequenceDiagram
+  participant C as Client
+  participant L as Leader
+  participant F1 as Follower 1
+  participant F2 as Follower 2
+
+  C->>L: Command X
+  L->>L: Append to log (index 5, term 3)
+  L->>F1: AppendEntries(index 5, term 3, X)
+  L->>F2: AppendEntries(index 5, term 3, X)
+  F1-->>L: Success
+  F2-->>L: Success
+  Note over L: Majority replicated; commit index 5
+  L->>L: Apply X to state machine
+  L-->>C: Result

.mermaid_validate/b0001.svg

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+flowchart LR
+    CLIENT[Client] -->|write x=5| N1[Node 1<br/>x=5]
+    N1 -->|replicate| N2[Node 2<br/>x=5 or x=?]
+    N1 -->|replicate| N3[Node 3<br/>x=5 or x=?]
+    CLIENT2[Another Client] -->|read x| N2